Favourite parts with off-label uses?

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

Cheers

Phil Hobbs
(*) who may be bulegoge's good twin, given the similarity of their emails

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[mpm]

On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

The Skyworks SKY66318-11 (3300-3600 MHz instantaneous bandwidth, high-efficiency, linearized RF power amplifier) makes a pretty good fuse.

 

[bitrex]

On 4/4/2020 8:49 PM, pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

Cheers

Phil Hobbs
(*) who may be bulegoge's good twin, given the similarity of their emails

The TL431 can be used as a multiple-feedback filter real easy
particularly with a 5 volt supply; the 2.5 volt reference is the
"virtual ground" and you only need the inverting input. keeping in mind
its adjust pin draws more current, 10s of microamps, than the average
bipolar op amp.

Common-anode 7 segment red LED display and 5 volt supply just use a
TL431 connected two-terminal between the display anode and supply and
drive the segments to ground with a uP, constant voltage and no
current-limiting resistors needed. Seems to be just about the right
brightness and very temperature stable with every red 7 segment I've tried.

kind of like toilet paper, duct tape, and WD-40 as a lubricant, the
TL431 is good at many tasks except the one it says on the label.

The LM386 is good for driving small brushed DC motors and the DIP
package can dissipate a lot of power and is very rugged. (thought I
guess that's technically in the data sheet but not really elaborated on)

 

[Ricky C]

On Saturday, April 4, 2020 at 10:43:46 PM UTC-4, mpm wrote:

On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:
Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

The Skyworks SKY66318-11 (3300-3600 MHz instantaneous bandwidth, high-efficiency, linearized RF power amplifier) makes a pretty good fuse.

What exactly are you trying to protect, a Littelfuse Polysorb?

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[whit3rd]

On Saturday, April 4, 2020 at 5:49:22 PM UTC-7, pcdh...@gmail.com wrote:

> Many of us use parts off-label, often very successfully

I'm fond of transistors, diode-wired, for thermometry. As an added
fillip, one can make a current-source two wire sensor by biasing the
sense diode with a four-wire fleapower regulator (1.2V feedback pin)
powering both a load resistor and a pullup/pulldown pair (resistor
pullup, resistor series with diode pulldown) to divide down and connect
at the feedback pin. The regulator input current then is a function of
the temperature, and independent of wiring resistance.

Another favorite off-label item, is an air-core inductor with a one-cent
coin in the middle. Lots of current for a millisecond, and... shrunken coin.
With enough power, shrunken quarter.

And if you ever need a bright point source, pencil leads only need a few
volts to make a fine little arc lamp.

 

On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

An LED can be used as the voltage reference for an NPN current source.
The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

Surface-mount platinum RTDs can be used in experiments, as both heater
and sensor, to quantify resistor heat sinking and thermal transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as constant-current
things. Tempcos are not great. The same diode can charge and discharge
a capacitor.

Some self-protecting SSRs can be used as electronic fuses. As can a 3t
regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a current
sink.

A bit of open-load transmission line can be a high-frequency peaker. I
have that option in my GHz o/e layout.

Someone said never use an opamp as a comparator. They were wrong.

An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make awesome
drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Microwave MMICS can be fabulous pulse amplifiers.

Zeners are good noise generators.

3t regulators can be good power amplifiers

Phemts can make amazing diodes. Too bad they are mostly gone.

Inside an FPGA, a dual-port sram can make an otherwise impossible
giant crossbar switch.

LVDS inputs on an FPGA make OK comparators.

Violating setup/hold specs on fast flipflops can be interesting.

Gates are delay lines.

One dual optocoupler can make a great high voltage amplifier output
stage. No level shifting problems.

PV optocouplers can be used as floating power supplies.

Unshielded drum-core inductors can be mag field sensors or
high-voltage signal/power isolators.

A toroidal inductor can be a liquid level sensor.

Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or
use a high resistance pot as an SPDT on-off-on switch.

Why are there no surface-mount fans?





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-04-04 22:43, mpm wrote:

On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:
Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

The Skyworks SKY66318-11 (3300-3600 MHz instantaneous bandwidth, high-efficiency, linearized RF power amplifier) makes a pretty good fuse.



I feel your pain.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote:
On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few
examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is
around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.


74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is
almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO
regulators with ceramic output caps. (It's good to be able to
disconnect the supplies during bring-up, and putting the jumper
between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

I've used them like that at your suggestion. Snazzy if you don't need
super low offset voltage. (And if you do, every comparator slows way down.)


An LED can be used as the voltage reference for an NPN current
source. The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

That's interesting. I recall discussing some very expensive parts sold
specifically for DC isolating thermal pours.


Surface-mount platinum RTDs can be used in experiments, as both
heater and sensor, to quantify resistor heat sinking and thermal
transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as
constant-current things. Tempcos are not great. The same diode can
charge and discharge a capacitor.

Interesting. Are they reasonably repeatable unit-to-unit?

For modest values of reasonable. It's Is, which is huge for
schottkies, hundred nA sorts of numbers. I've posted my RF detector
which is a diode and a capacitor. It's in production.

Some self-protecting SSRs can be used as electronic fuses. As can a
3t regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a
current sink.



A bit of open-load transmission line can be a high-frequency peaker.
I have that option in my GHz o/e layout.

Interesting. How does that work? Normally I think of O/C tlines as a
series resonance to ground.

Stick a drooling-rise step into one end of a transmission line and it
will overshoot and snap up the waveform at the other end. Adjust the
source impedance, or terminate a little, to trim the step response.
It's sharper than RC peaking, so compensates things like Ft rolloff or
skin effect.

I had a profound, life-changing revelation recently. If you don't poke
a fast rise into a passive transmission line, you won't get a fast
reflection. I wasted all those years designing absorptive lowpass
filters.

Someone said never use an opamp as a comparator. They were wrong.

Gotta watch for the antiparallel diodes on the inputs, though. For slow
stuff, LM358s work great as comparators--the inputs survive going way
above the supply.


An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make
awesome drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Annoying that they don't tell you k in the datasheet, and you can't even
back it out from the series-connected inductance, which is quoted as
exactly four times the parallel-connected value.

The k's are really high. Easy to measure.

Microwave MMICS can be fabulous pulse amplifiers.

Zeners are good noise generators.

3t regulators can be good power amplifiers

Phemts can make amazing diodes. Too bad they are mostly gone.

Well, MCL is pretty good about keeping stuff in production.

Yes, but they are little ones. The Avago SOT89s were great 1 amp, 1
pF, zero recovery diodes.

Inside an FPGA, a dual-port sram can make an otherwise impossible
giant crossbar switch.

LVDS inputs on an FPGA make OK comparators.

Violating setup/hold specs on fast flipflops can be interesting.

How so?

We are measuring timings and jitter to fs resolution by sweeping one
edge across another, clock and D on a GigaComm flipflop, and averaging
the Q output. I have some data if anyone's interested.

Gates are delay lines.

Poorly specified ones, though--at least in 74HC, typical propagation
delay specs are half of the maximum. Of course, my usual rule for
one-shots is to avoid them unless the circuit would be okay over a 3:1
range of delays.

That's often all you need, some sort of glitch.

One dual optocoupler can make a great high voltage amplifier output
stage. No level shifting problems.

PV optocouplers can be used as floating power supplies.

Unshielded drum-core inductors can be mag field sensors or
high-voltage signal/power isolators.

A toroidal inductor can be a liquid level sensor.

That one I haven't heard about. Are you looking for the NMR signal?

A conductive liquid is a shorted turn.

Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or
use a high resistance pot as an SPDT on-off-on switch.

BTW, did you find a good replacement for that discontinued Murata PV2A
one that works up to 1-2 GHz?

Don't think so. I'll check. Production hates them... hard to adjust.

Why are there no surface-mount fans?

Dunno, but maybe because high temperature engineering plastic is
expensive. You could probably make them with graphite block bearings.

We're putting fans on PCBs with angle brackets. A fan blowing directly
on parts is wonderful thermally. Almost like they designed them to do
that.

They could also put tapped holes at 90 degrees.

Cheers

Phil Hobbs

--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote:

On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few
examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is
around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.


74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is
almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO
regulators with ceramic output caps. (It's good to be able to
disconnect the supplies during bring-up, and putting the jumper
between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

I've used them like that at your suggestion. Snazzy if you don't need
super low offset voltage. (And if you do, every comparator slows way down.)

An LED can be used as the voltage reference for an NPN current
source. The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

That's interesting. I recall discussing some very expensive parts sold
specifically for DC isolating thermal pours.

Surface-mount platinum RTDs can be used in experiments, as both
heater and sensor, to quantify resistor heat sinking and thermal
transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as
constant-current things. Tempcos are not great. The same diode can
charge and discharge a capacitor.

Interesting. Are they reasonably repeatable unit-to-unit?

Some self-protecting SSRs can be used as electronic fuses. As can a
3t regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a
current sink.

A bit of open-load transmission line can be a high-frequency peaker.
I have that option in my GHz o/e layout.

Interesting. How does that work? Normally I think of O/C tlines as a
series resonance to ground.

Someone said never use an opamp as a comparator. They were wrong.

Gotta watch for the antiparallel diodes on the inputs, though. For slow
stuff, LM358s work great as comparators--the inputs survive going way
above the supply.

An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make
awesome drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Annoying that they don't tell you k in the datasheet, and you can't even
back it out from the series-connected inductance, which is quoted as
exactly four times the parallel-connected value.

Microwave MMICS can be fabulous pulse amplifiers.

Zeners are good noise generators.

3t regulators can be good power amplifiers

Phemts can make amazing diodes. Too bad they are mostly gone.

Well, MCL is pretty good about keeping stuff in production.

Inside an FPGA, a dual-port sram can make an otherwise impossible
giant crossbar switch.

LVDS inputs on an FPGA make OK comparators.

Violating setup/hold specs on fast flipflops can be interesting.

How so?

Gates are delay lines.

Poorly specified ones, though--at least in 74HC, typical propagation
delay specs are half of the maximum. Of course, my usual rule for
one-shots is to avoid them unless the circuit would be okay over a 3:1
range of delays.

One dual optocoupler can make a great high voltage amplifier output
stage. No level shifting problems.

PV optocouplers can be used as floating power supplies.

Unshielded drum-core inductors can be mag field sensors or
high-voltage signal/power isolators.

A toroidal inductor can be a liquid level sensor.

That one I haven't heard about. Are you looking for the NMR signal?

Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or
use a high resistance pot as an SPDT on-off-on switch.

BTW, did you find a good replacement for that discontinued Murata PV2A
one that works up to 1-2 GHz?

Why are there no surface-mount fans?

Dunno, but maybe because high temperature engineering plastic is
expensive. You could probably make them with graphite block bearings.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-04-05 11:42, jlarkin@highlandsniptechnology.com wrote:

On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote:
On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few
examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is
around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.


74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is
almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO
regulators with ceramic output caps. (It's good to be able to
disconnect the supplies during bring-up, and putting the jumper
between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

I've used them like that at your suggestion. Snazzy if you don't need
super low offset voltage. (And if you do, every comparator slows way down.)


An LED can be used as the voltage reference for an NPN current
source. The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

That's interesting. I recall discussing some very expensive parts sold
specifically for DC isolating thermal pours.


Surface-mount platinum RTDs can be used in experiments, as both
heater and sensor, to quantify resistor heat sinking and thermal
transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as
constant-current things. Tempcos are not great. The same diode can
charge and discharge a capacitor.

Interesting. Are they reasonably repeatable unit-to-unit?

For modest values of reasonable. It's Is, which is huge for
schottkies, hundred nA sorts of numbers. I've posted my RF detector
which is a diode and a capacitor. It's in production.



Some self-protecting SSRs can be used as electronic fuses. As can a
3t regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a
current sink.



A bit of open-load transmission line can be a high-frequency peaker.
I have that option in my GHz o/e layout.

Interesting. How does that work? Normally I think of O/C tlines as a
series resonance to ground.

Stick a drooling-rise step into one end of a transmission line and it
will overshoot and snap up the waveform at the other end. Adjust the
source impedance, or terminate a little, to trim the step response.
It's sharper than RC peaking, so compensates things like Ft rolloff or
skin effect.

Okay, so not really open-circuited. I'll try it out. That could
potentially have helped that single-diode sampler gizmo--its speed was
limited by the rise time of the line receiver driving the pHEMT switch.
That one used a capacitor plus a short, mismatched shunt stub to make
the sampling pulse from a falling edge.

I had a profound, life-changing revelation recently. If you don't poke
a fast rise into a passive transmission line, you won't get a fast
reflection. I wasted all those years designing absorptive lowpass
filters.

Gasp!

Someone said never use an opamp as a comparator. They were wrong.

Gotta watch for the antiparallel diodes on the inputs, though. For slow
stuff, LM358s work great as comparators--the inputs survive going way
above the supply.


An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make
awesome drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Annoying that they don't tell you k in the datasheet, and you can't even
back it out from the series-connected inductance, which is quoted as
exactly four times the parallel-connected value.

The k's are really high. Easy to measure.

That's unusual for a 'coupled inductor'. I normally expect it to be
around 0.85.

Microwave MMICS can be fabulous pulse amplifiers.

Zeners are good noise generators.

3t regulators can be good power amplifiers

Phemts can make amazing diodes. Too bad they are mostly gone.

Well, MCL is pretty good about keeping stuff in production.

Yes, but they are little ones. The Avago SOT89s were great 1 amp, 1
pF, zero recovery diodes.

Ah, okay.

Inside an FPGA, a dual-port sram can make an otherwise impossible
giant crossbar switch.

LVDS inputs on an FPGA make OK comparators.

Violating setup/hold specs on fast flipflops can be interesting.

How so?

We are measuring timings and jitter to fs resolution by sweeping one
edge across another, clock and D on a GigaComm flipflop, and averaging
the Q output. I have some data if anyone's interested.

Right, I saved the schematic from when you posted it awhile back (2014).
That was a 10EP52, which is now available only from Rochester. I'd be
interested in the data and the updated version, sure. I'm sure I'll
need to do that one of these days.

Gates are delay lines.

Poorly specified ones, though--at least in 74HC, typical propagation
delay specs are half of the maximum. Of course, my usual rule for
one-shots is to avoid them unless the circuit would be okay over a 3:1
range of delays.


That's often all you need, some sort of glitch.



One dual optocoupler can make a great high voltage amplifier output
stage. No level shifting problems.

PV optocouplers can be used as floating power supplies.

Unshielded drum-core inductors can be mag field sensors or
high-voltage signal/power isolators.

A toroidal inductor can be a liquid level sensor.

That one I haven't heard about. Are you looking for the NMR signal?

A conductive liquid is a shorted turn.

At sufficiently low frequency, anyway.

We've started putting little Sensirion T/H sensors in a lot of things.
When using TECs, it's awfully nice to be able to compute the dew point,
for instance, and in outdoor applications (e.g. our fire sensors for
harvesters) it's good to be able to predict when the window is liable to
fog up on the inside.

We use IP67+ enclosures with bags of 5A molecular sieve inside, which is
super cheap and will absorb 50% of its own mass in water. Simon has had
to learn a whole lot about enclosures and mechanical design generally.
Turns out that you have to put an air vent on the enclosure to prevent
pumping water inside due to atmospheric pressure differences. That
leads to working of the O-ring seals, which wears them out.

We considered using a bellows, but atmospheric pressure varies +-7% or
so, which makes for a pretty big, floppy bellows. Hermetic construction
is possible but very expensive, and relies on glass or ceramic insulated
connectors. The glass would have had to be brazed or indium-soldered to
the lid, which leads to CTE mismatch problems.

Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or
use a high resistance pot as an SPDT on-off-on switch.

BTW, did you find a good replacement for that discontinued Murata PV2A
one that works up to 1-2 GHz?

Don't think so. I'll check. Production hates them... hard to adjust.

Yup. Hard to replace for times you need them, though, e.g. gain peaking
tweaks. You aren't doing that with a dpot.

Why are there no surface-mount fans?

Dunno, but maybe because high temperature engineering plastic is
expensive. You could probably make them with graphite block bearings.

We're putting fans on PCBs with angle brackets. A fan blowing directly
on parts is wonderful thermally. Almost like they designed them to do
that.

They could also put tapped holes at 90 degrees.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

On Sun, 5 Apr 2020 12:17:03 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-05 11:42, jlarkin@highlandsniptechnology.com wrote:
On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote:
On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few
examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is
around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.


74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is
almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO
regulators with ceramic output caps. (It's good to be able to
disconnect the supplies during bring-up, and putting the jumper
between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

I've used them like that at your suggestion. Snazzy if you don't need
super low offset voltage. (And if you do, every comparator slows way down.)


An LED can be used as the voltage reference for an NPN current
source. The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

That's interesting. I recall discussing some very expensive parts sold
specifically for DC isolating thermal pours.


Surface-mount platinum RTDs can be used in experiments, as both
heater and sensor, to quantify resistor heat sinking and thermal
transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as
constant-current things. Tempcos are not great. The same diode can
charge and discharge a capacitor.

Interesting. Are they reasonably repeatable unit-to-unit?

For modest values of reasonable. It's Is, which is huge for
schottkies, hundred nA sorts of numbers. I've posted my RF detector
which is a diode and a capacitor. It's in production.



Some self-protecting SSRs can be used as electronic fuses. As can a
3t regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a
current sink.



A bit of open-load transmission line can be a high-frequency peaker.
I have that option in my GHz o/e layout.

Interesting. How does that work? Normally I think of O/C tlines as a
series resonance to ground.

Stick a drooling-rise step into one end of a transmission line and it
will overshoot and snap up the waveform at the other end. Adjust the
source impedance, or terminate a little, to trim the step response.
It's sharper than RC peaking, so compensates things like Ft rolloff or
skin effect.

Okay, so not really open-circuited. I'll try it out. That could
potentially have helped that single-diode sampler gizmo--its speed was
limited by the rise time of the line receiver driving the pHEMT switch.
That one used a capacitor plus a short, mismatched shunt stub to make
the sampling pulse from a falling edge.

The soft peaking helps when a step has a soft corner on the rise,
which is very common. That's why people who do fast stuff cheat and
measure risetime 20/80.

I had a profound, life-changing revelation recently. If you don't poke
a fast rise into a passive transmission line, you won't get a fast
reflection. I wasted all those years designing absorptive lowpass
filters.

Gasp!





Someone said never use an opamp as a comparator. They were wrong.

Gotta watch for the antiparallel diodes on the inputs, though. For slow
stuff, LM358s work great as comparators--the inputs survive going way
above the supply.


An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make
awesome drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Annoying that they don't tell you k in the datasheet, and you can't even
back it out from the series-connected inductance, which is quoted as
exactly four times the parallel-connected value.

The k's are really high. Easy to measure.

That's unusual for a 'coupled inductor'. I normally expect it to be
around 0.85.

The DRQs are bifilar. Two or three 9's.

And a lot of capacitance. They make nice autotransformer flybacks.
Does that have a better name?

A toroidal inductor can be a liquid level sensor.

That one I haven't heard about. Are you looking for the NMR signal?

A conductive liquid is a shorted turn.

At sufficiently low frequency, anyway.

We've started putting little Sensirion T/H sensors in a lot of things.
When using TECs, it's awfully nice to be able to compute the dew point,
for instance, and in outdoor applications (e.g. our fire sensors for
harvesters) it's good to be able to predict when the window is liable to
fog up on the inside.

We use IP67+ enclosures with bags of 5A molecular sieve inside, which is
super cheap and will absorb 50% of its own mass in water. Simon has had
to learn a whole lot about enclosures and mechanical design generally.
Turns out that you have to put an air vent on the enclosure to prevent
pumping water inside due to atmospheric pressure differences. That
leads to working of the O-ring seals, which wears them out.

We considered using a bellows, but atmospheric pressure varies +-7% or
so, which makes for a pretty big, floppy bellows. Hermetic construction
is possible but very expensive, and relies on glass or ceramic insulated
connectors. The glass would have had to be brazed or indium-soldered to
the lid, which leads to CTE mismatch problems.

A balloon inside?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[whit3rd]

On Sunday, April 5, 2020 at 8:42:58 AM UTC-7, jla...@highlandsniptechnology.com wrote:

On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2020-04-05 00:09, jla...@highlandsniptechnology.com wrote:

Why are there no surface-mount fans?

Dunno, but maybe because high temperature engineering plastic is
expensive. You could probably make them with graphite block bearings.

We're putting fans on PCBs with angle brackets. A fan blowing directly
on parts is wonderful thermally. Almost like they designed them to do
that.

Historically, if the parts might be muffins, they did.
The surface-flow fans on high-end video cards are axial-in/circumference-out
air movers, a variant on the bottom-sucking sump pump designs of
indeterminate age. Ducting (housing) gets in the way of IR for surface-mount
parts, even if you can afford the materials.

So, you'd want to surface-mount a connector at the western edge of the footprint,
and rout an aperture (or apertures) at the eastern edge, then after reflow, the
fan hooks onto the aperture and swings down to mate with the connector.
Wire-tie or latching connector keep it in place.

Or glue... but moving parts are best kept replaceable.

 

[George Herold]

On Sunday, April 5, 2020 at 12:09:59 AM UTC-4, jla...@highlandsniptechnology.com wrote:

On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.


74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

An LED can be used as the voltage reference for an NPN current source.
The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

Surface-mount platinum RTDs can be used in experiments, as both heater
and sensor, to quantify resistor heat sinking and thermal transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as constant-current
things. Tempcos are not great. The same diode can charge and discharge
a capacitor.

Some self-protecting SSRs can be used as electronic fuses. As can a 3t
regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a current
sink.

A bit of open-load transmission line can be a high-frequency peaker. I
have that option in my GHz o/e layout.

Someone said never use an opamp as a comparator. They were wrong.

An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make awesome
drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Microwave MMICS can be fabulous pulse amplifiers.

Zeners are good noise generators.

3t regulators can be good power amplifiers

Phemts can make amazing diodes. Too bad they are mostly gone.

Inside an FPGA, a dual-port sram can make an otherwise impossible
giant crossbar switch.

LVDS inputs on an FPGA make OK comparators.

Violating setup/hold specs on fast flipflops can be interesting.

Gates are delay lines.

One dual optocoupler can make a great high voltage amplifier output
stage. No level shifting problems.

PV optocouplers can be used as floating power supplies.

Unshielded drum-core inductors can be mag field sensors or
high-voltage signal/power isolators.

A toroidal inductor can be a liquid level sensor.

Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or
use a high resistance pot as an SPDT on-off-on switch.

Why are there no surface-mount fans?
Oh nice. Reverse biased (red GaAs) led's as single photon detectors.

George H.

--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

NXP 74aup2g07 - analog switch
https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf

 

[George Herold]

On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable.

74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit.

Your faves?

Wow nice list!
I'd like to take a 'part' off the alt. use list.
I use to tout the use of 20 zeners rev biased at ~10-100 uA
as audio noise sources. When I went to replace the pack I had
it turned out I had a 'golden string'. I had to order a bunch
from different suppliers to find noisy batch. (And that still wasn't as
good(noisy) as the original... but it's obvious that almost no one wants
a noisy zener.)

George H.

Cheers

Phil Hobbs
(*) who may be bulegoge's good twin, given the similarity of their emails

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[George Herold]

On Sunday, April 5, 2020 at 11:42:58 AM UTC-4, jla...@highlandsniptechnology.com wrote:

On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote:
On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote:

Following up on blocher's sterling work,(*)

Many of us use parts off-label, often very successfully. A few
examples:

SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is
around 12 GHz, but they're amazingly stable.

They make excellent switches too. Rds-on is never specified for RF
parts, but it's about 2 ohms for the 551.


74HC4352s make good flying-capacitor diff amp front ends.

TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is
almost in a class with relays, but 1E5 times faster.

Zero-ohm jumpers have about the right resistance to stabilize LDO
regulators with ceramic output caps. (It's good to be able to
disconnect the supplies during bring-up, and putting the jumper
between the reg and the output cap has this additional benefit.

Your faves?

Some digital bus and USB switches are cheap and are excellent,
super-fast analog multiplexers.

Some chips are useful just for their ESD diodes.

LVDS line receivers are super-fast, dirt cheap RRIO comparators.

I've used them like that at your suggestion. Snazzy if you don't need
super low offset voltage. (And if you do, every comparator slows way down.)


An LED can be used as the voltage reference for an NPN current
source. The tempcos can be made to almost cancel.

High value AlN resistors can be used as thermal bridges.

That's interesting. I recall discussing some very expensive parts sold
specifically for DC isolating thermal pours.


Surface-mount platinum RTDs can be used in experiments, as both
heater and sensor, to quantify resistor heat sinking and thermal
transients.

Surface-mount resistors can be last-resort fuses.

Low-barrier schottky diodes can be used in reverse as
constant-current things. Tempcos are not great. The same diode can
charge and discharge a capacitor.

Interesting. Are they reasonably repeatable unit-to-unit?

For modest values of reasonable. It's Is, which is huge for
schottkies, hundred nA sorts of numbers. I've posted my RF detector
which is a diode and a capacitor. It's in production.



Some self-protecting SSRs can be used as electronic fuses. As can a
3t regulator with the adj pin open.

Depletion fets are nice capacitor bleeders. Ditto 3t reg as a
current sink.



A bit of open-load transmission line can be a high-frequency peaker.
I have that option in my GHz o/e layout.

Interesting. How does that work? Normally I think of O/C tlines as a
series resonance to ground.

Stick a drooling-rise step into one end of a transmission line and it
will overshoot and snap up the waveform at the other end. Adjust the
source impedance, or terminate a little, to trim the step response.
It's sharper than RC peaking, so compensates things like Ft rolloff or
skin effect.

I had a profound, life-changing revelation recently. If you don't poke
a fast rise into a passive transmission line, you won't get a fast
reflection. I wasted all those years designing absorptive lowpass
filters.




Someone said never use an opamp as a comparator. They were wrong.

Gotta watch for the antiparallel diodes on the inputs, though. For slow
stuff, LM358s work great as comparators--the inputs survive going way
above the supply.


An rro opamp can also be used as a current limiter/fuse.

You can do all sorts of things with ribbon cable.

Some HV diodes and the c-b junctions of some transistors make
awesome drift step-recovery (Grehkov) diodes.

BFT25s can be used as fA-leakage diodes.

Dual-winding inductors, like DRQ127, can do all kinds of tricks.

Annoying that they don't tell you k in the datasheet, and you can't even
back it out from the series-connected inductance, which is quoted as
exactly four times the parallel-connected value.

The k's are really high. Easy to measure.


Microwave MMICS can be fabulous pulse amplifiers.

Zeners are good noise generators.

3t regulators can be good power amplifiers

Phemts can make amazing diodes. Too bad they are mostly gone.

Well, MCL is pretty good about keeping stuff in production.

Yes, but they are little ones. The Avago SOT89s were great 1 amp, 1
pF, zero recovery diodes.



Inside an FPGA, a dual-port sram can make an otherwise impossible
giant crossbar switch.

LVDS inputs on an FPGA make OK comparators.

Violating setup/hold specs on fast flipflops can be interesting.

How so?

We are measuring timings and jitter to fs resolution by sweeping one
edge across another, clock and D on a GigaComm flipflop, and averaging
the Q output. I have some data if anyone's interested.



Gates are delay lines.

Poorly specified ones, though--at least in 74HC, typical propagation
delay specs are half of the maximum. Of course, my usual rule for
one-shots is to avoid them unless the circuit would be okay over a 3:1
range of delays.


That's often all you need, some sort of glitch.



One dual optocoupler can make a great high voltage amplifier output
stage. No level shifting problems.

PV optocouplers can be used as floating power supplies.

Unshielded drum-core inductors can be mag field sensors or
high-voltage signal/power isolators.

A toroidal inductor can be a liquid level sensor.

That one I haven't heard about. Are you looking for the NMR signal?

A conductive liquid is a shorted turn.

Huh, that's fun. you could play with the frequency.
I had an axial inductor, (audio) Q went to hell after a
water bath flux wash. I got better when dry, but took a while.
(once found inductor was no longer immersed in water.)

George H.

Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or
use a high resistance pot as an SPDT on-off-on switch.

BTW, did you find a good replacement for that discontinued Murata PV2A
one that works up to 1-2 GHz?

Don't think so. I'll check. Production hates them... hard to adjust.



Why are there no surface-mount fans?

Dunno, but maybe because high temperature engineering plastic is
expensive. You could probably make them with graphite block bearings.

We're putting fans on PCBs with angle brackets. A fan blowing directly
on parts is wonderful thermally. Almost like they designed them to do
that.

They could also put tapped holes at 90 degrees.


Cheers

Phil Hobbs


--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Ricky C]

On Sunday, April 5, 2020 at 3:43:32 PM UTC-4, plastco...@gmail.com wrote:

NXP 74aup2g07 - analog switch
https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf

How exactly does that work?

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

On Sun, 5 Apr 2020 12:43:27 -0700 (PDT), plastcontrol.ru@gmail.com
wrote:

NXP 74aup2g07 - analog switch
https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf

Those are great. I use them to discharge the cap in precision
linear-ramp timing circuits.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Clifford Heath]

On 6/4/20 10:12 am, jlarkin@highlandsniptechnology.com wrote:

On Sun, 5 Apr 2020 12:43:27 -0700 (PDT), plastcontrol.ru@gmail.com
wrote:

NXP 74aup2g07 - analog switch
https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf

Those are great. I use them to discharge the cap in precision
linear-ramp timing circuits.

I know you're concerned about the C-V curve with your fast ramps. How
does this device stack up (against your fave pHEMTs for example)>

Clifford Heath

 

[whit3rd]

On Sunday, April 5, 2020 at 5:12:12 PM UTC-7, jla...@highlandsniptechnology.com wrote:

On Sun, 5 Apr 2020 12:43:27 -0700 (PDT), plastcontrol.ru@gmail.com
wrote:

NXP 74aup2g07 - analog switch
https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf

Those are great. I use them to discharge the cap in precision
linear-ramp timing circuits.

The traditional way to discharge the cap would be a controlled current source, and
you take the zero-crossing time to indicate the state of charge instead of using
a fast ADC. That way, all cycles discharge the capacitor to the exact same level.