audio recording on IC -help wanted

[Paul]

On Jun 22, 9:15 am, "Helmut Sennewald" <helmutsennew...@t-online.de>
wrote:

"Paul" <energymo...@gmail.com> schrieb im Newsbeitragnews:d46baf44-9ad4-4d95-a262-a427a3bbc7f4@u12g2000prd.googlegroups.com...





On Jun 22, 3:23 am, "Helmut Sennewald" <helmutsennew...@t-online.de
wrote:
"Paul" <energymo...@gmail.com> schrieb im
Newsbeitragnews:c8301dfa-b8fd-47e0-8aac-7f028584b21d@j1g2000prb.googlegroups.com...

On Jun 21, 8:41 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
On Sat, 21 Jun 2008 08:25:59 -0700 (PDT), Paul <energymo...@gmail.com
wrote:

Hi,

As you know, the *input* offset voltage is the voltage required
across
the op-amp's input terminals to drive the output voltage to zero.
Although it has been my experience that for most op-amps the input
offset voltage is due to the "-" input pin for the *most* part. For
example, according to Spice the input offset voltage on the "+" input
pin on a LMC660A op-amp for a non-inverting amp circuit is a few
nanovolts, disregarding thermoelectric effects mind you, but a few
millivolts on the "-" input pin. Although as you know the input
signal
is not applied to the "-" input pin for a non-inverting amp circuit,
which means there's just a few nanovolts on the input of such a
circuit if we disregard thermoelectric effects.

The offset voltage is *differential*. You can blame it on either pin,
or both pins... it doesn't matter who you blame, the result is the
same: offset voltage becomes measurement error.

I have a INA116PA Instrumentation op-amp where Ib typ = 3fA, Ib max =
25fA, and Vos typ = 0.5mV. Now it seems to me in order for there to
be
0.5mV on the input of this Instrumentation op-amp circuit with 3fA
bias current that the DUT input impedance would have to be 0.50mV /
3.0fA = 170 Gohms. On the other hand, if the DUT input impedance is
say 200 Kohms then would the input offset voltage be 3.0fA * 200Kohms
= 0.6nV, disregarding thermoelectric effects?

The offset voltage error is a different thing from the input bias
current. They are unrelated [1]. You can of course generate a real,
external-to-the-opamp error voltage by dumping the bias current into
real external resistance, but that's a different matter entirely.

John

[1] Some opamps have low offsets and high bias currents, and some vice
versa. Chopper amps are low on both; cheap bipolars are high on both.

The LMC660A has a typical voltage offset of 1mV and bias current of
2fA, but that depends what type of op-amp circuit. According to Spice
the input voltage offset for an inverting or differential circuit is
about what the Vos spec says, but for a non-inverting circuit it's a
few nanovolts on the "+" input pin. I'm wondering if the Vos in
datasheets is referring to a certain type of op-amp circuit such as
the inverting type (http://hyperphysics.phy-astr.gsu.edu/Hbase/
Electronic/opampvar.html#c2).

Regards,
Paul

Hello Paul,
Maybe it helps if you think about the transistor circuit
of an opamp.

The first stage of an opamp consists of a differential
amplifier made by a pair of two well matched transistors.
The difference of the Vgs(Mosfet opamp) or Vbe(bipolar opamp)
of these two transistors in the input stage is the main
contributor for the offset voltage.

Offset voltage is always measured between the + and - input.
What you have measured at the +input is the bias(leakage)
current multiplied by the value of the resistor connected
to the +pin.

Best regards,
Helmut- Hide quoted text -

I appreciate all of the replies! All of these years I've had this
false idea about the datasheets Vos burnt into my head. I've always
assumed that if the datasheet said the op-amps Vos was say 50uV then
that's the lowest input voltage (by my def: the voltage applied on the
input device due to the op-amp) one can expect with a typical op-amp
circuit such as an inverter or non-inverter.

So it's true that one could achieve input voltages in the nanovolt
region on a 200K ohm DUT from an Instrumentation op-amp chip such as
INA116PA even though the datasheet Vos spec is 2mV?

Thanks,
Paul

INA116PA datasheet:
http://focus.ti.com/lit/ds/symlink/ina116.pdf

Hello Paul,

Yes you can apply voltages as small as you like.
they will be still amplified by the gain G, set with
the feedback resistors. The drawback of any Vos
is that you will have an output voltage of (Vos+Vin)*G .
This menas you have to either adjust the offset voltage
already at the input or you have to subtract Vos*G at
the output.

Best regards,
Helmut- Hide quoted text -

Thanks! As you said the output offset can always be corrected, but
it's great to know that a 2mV op-amp chip such as the INA116PA can
apply DC voltages as low as a few nanovolts on the input device
without adding shunt resistors. Of course one can always add a shunt
resistor to lower the input voltage across the DUT, something I knew
about, but of course that has obvious effects of decreasing the DUT's
effective input voltage to the op-amp.

I'm wondering if there are any op-amps or perhaps a BiFET amp circuit
that could achieve a few nanovolts across say a 200K ohm device while
consuming no more than a few microwatts. The idea is that such a
microwatt amp would have considerably less input thermoelectric
effects. Thermoelectric effects can generate a half dozen or more
microvolts on the DUT unless carefully balanced with dummy resistors.
I believe Linear Tech has some microwatt op-amps, but nothing near
25fA bias current.

Thanks,
Paul

 

[EePee]

Has anybody this datasheet to copy?

Kindly, EePee.

 

[JW]

On Thu, 05 Jun 2008 11:46:19 -0400 legg <legg@nospam.magma.ca> wrote in
Message id: <8d1g441grjog0lgvd15uu1vdk5amasf466@4ax.com>:

On Thu, 05 Jun 2008 06:36:33 -0400, JW <none@dev.nul> wrote:

On Tue, 03 Jun 2008 05:33:30 -0400 JW <none@dev.nul> wrote in Message id:
sp3a4458nqv40cu7tgjmd5i76cjdiv7f4n@4ax.com>:

On Mon, 2 Jun 2008 11:25:18 -0700 dplatt@radagast.org (Dave Platt) wrote
in Message id: <ehqdh5-spo.ln1@radagast.org>:

In article <n9g7445fdmof3nohavnt74eghlh02mb0je@4ax.com>,
JW <none@dev.nul> wrote:

I think I'll try option 2 with a U441.

Yeah... that's certainly the sensible thing to do, unless you find
that the device *really* needs very specific selection for various
parameters.

Now for my dumb/ignorant question: The schematic does not show source and
drain - how do I determine which is which when I replace the part?

For an N-JFET, the source goes towards the more negative voltage...
in this schematic, it looks as if the downward side would be the
lower-voltage side per the normal convention, and thus the drain's on
the top and the source is on the bottom.

JFETs tend to be fairly symmetrical, and will often work if you swap
the source and drain, but since the source/gate and drain/gate
capacitances may not be identical you should probably keep the part in
its preferred orientation.

Hello Dave,

Excellent. Many thanks for your help and valuable lesson. I've ordered the
part from Newark and will reply back and let you know how it went.


Well, got the device in and installed in the circuit. It was pretty close,
but I couldn't make it through the input stage balancing procedure on pg.
143 and 144 of the service manual:

http://www.keithley.com/data?asset=1062

I followed the procedure for setting jumper W303 (in my case position C
was required) and could only get the display to read about 18mV when
adjusting R314. So, I tweaked R351 a bit lower and managed to get it down
to 0.0mV when adjusting R314, but it wasn't stable - it would drift around
one or two millivolts or so.

At this point, I took a "known-good" instrument from stock, and verified
it's stability. I found it to be rock solid give or take ten microvolts or
so. I removed the JFET from the known-good unit and dropped it into the
unit I was repairing. I put R351 back to it's stock resistance of 16.5K.
This fixed the unit. Since the customer was getting (very) impatient and
my boss was willing to sacrifice our unit for the time being, I finished
calibrating it and shipped it off yesterday. Of course, now *our*
"known-good" needs a replacement Q308 dual JFET.

Does anyone have any other possible subs I could try?


The U411 wasn't specified for low gate leakage (~200pA), and may be in
the wrong package (TO71 - 6pin TO18) to provide this. Most of the
low-leakage duals ( 1 to 5 pA) are in the larger TO78 (6pin TO5) case
sizes.

U421 through U428 are all below 5pA. If you move to the smaller can
size, the lreakage pec automatically increases by a factor of 5.

For a static match less than 25mV, you'd be restricted to U421/2/5/6.

The jedec low-leakage types are 2N5902-2N5909 inclusive (2 to 5pA),
all below 15mV match.

RL

Hello Legg,

Given the specs you mention WRT leakage, I managed to get a couple of
samples of an LS5907 from Linear systems that is rated at 150fA. This is
apparently a cross or the same as a 2N5907. The nice folks there sent 'em
to me for free. http://www.linearsystems.com/datasheets/LS5905-9.pdf
This device did the trick! Thank you very much, you've been extremely
helpful.

 

[Tim Schwartz]

N_Cook wrote:

Tim Schwartz <timhhk@verizon.net> wrote in message
news:485CED7A.3070402@verizon.net...
N_Cook wrote:
From the 1970s / 1980s. I have an RCA databook with a lot of the big
number
RCA transistor full data, but cannot find full data anywhere on these
1C..
ones , that is 1C ( one see) not IC ( India Charlie ).

Google, in half the hits seems, to show lesser data/ working subs I've
put
on the net over the years.

Just repaired a 1986 HH which used , no problem with it, 1C03-C which is
presumably a voltage binning band, but thought I'd try locating some
proper
info on this RCA range for when I need it in earnest.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/







Nigel,

From page 486 in the 1981 RCA Power Devices data book in my library:

"Silicon Transistors for Audio-Frequency Linear-Amplifier Applications"

RCA1C03 (NPN):
V(CBO) 120V
V(CEO) 100V
I(C) 4 amps
P(T) is 40 Watts with CASE temp at 25 decrees C.
F(T) 4 MHz
h(FE) 50-250


The RCA1C04 is the PNP compliment, specs the same except F(T)=5 MHz

The RCA1C012 (and compliment RCA1C013) are the same except the
V(CBO)=140V and the V(CEO)=120V. (They list these with and without the
'0' on the same page, so they might be called RCA1C12 and RCA1C13)

If you need the more detailed specs, let me know.

Regards,
Tim Schwartz
Bristol Electronics


Any reference to what the suffix C means in
RCA1C03-C

Vcb max of 120V times 2.5 = 300 volt seems unlikely


Nigel,

There is no reference to any suffix on the data sheet I have. (I can
fax you a copy if you e-mail me with a fax number.) Also, I'm not aware
that RCA ever used a 'multiplier'. Texas Instruments did on some
devices (like the TIP-31/31A/31B/31C) but I'm not aware that the suffix
was a multiplier. The data sheet always listed the specific voltage for
each version.

Regards,
Tim Schwartz
Bristol Electronics

 

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[Salmon Egg]

On 6/27/07 10:59 PM, in article
1183010366.572665.130500@a26g2000pre.googlegroups.com, "bubbles123"
<jglai16@gmail.com> wrote:

At the moment I'm just pulsing a 1MHz square wave through my IR
emitter but the output from the transimpedance amplifier does not come
out square! Can anyone suggest an IC transimpedance amp that will work
for 1MHz signals across an IR link? (the OPA380 has a 1MHz bandwidth -
hence the distortion at the output).
Why do you expect the output of the IR source to follow the input waveform

closely? It might, but that needs to be proven rather than assumed.

Bill
--
Iraq: About three Virginia Techs a month

 

[Joerg]

John Larkin wrote:

On Mon, 23 Jun 2008 13:00:04 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Ok, guys, we had a thread about NXP's site a while ago. Long story short
I wrote to them and, surprise, they engaged in a lively back-and-forth
improvement session and really listened. They changed a lot of stuff,
got rid of fluff and while not perfect yet I think the NXP site has
improved quite a bit. Heck, now you can even use it with Java Script
turned off (gets rid of the nag screen). And no, I am not paid by them,
just got involved because I didn't want to see a company that was good
to me go down the tubes.

http://www.nxp.com/indexnc.html

So what do thee think?


Better. I use Flashblock, and it doesn't even try anything tricky. The
structure is still pretty weird, though.

What is the "switch to classic mode/switch to liquid mode" thing at
the bottom?

Allows you to switch back to the old Philips-style site. At the end of
this improvement process they'll hopefully ditch that.

And "contact" should just provide email addresses, not the dumb form
to fill out.

I've told them

At least they still offer the wideband transistors!

Yes. What concerned me is that only two parts show up under analog.
Probably ended up in the wrong places but it'll be corrected.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

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[JW]

On Wed, 15 Aug 2007 00:29:50 GMT h.STOPgodavari@shaw.STOPca wrote in
Message id: <46C2491D.2ED06021@shaw.STOPca>:

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Bye.
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[Jim]

On 17 Jun 2007, mc <look@www.ai.uga.edu.for.address> wrote:

What would you use this for?

At the moment I can only think of the obvious application: bugging
other peoples conversations, something I'd not be happy to assist
with..

Good point, but he doesn't have to ask us for technical help for
that -- there are commercial gadgets available. At one time Radio
Shack sold one (in the USA).

I am the OP. Just to clarify ....

There are several ready-built gadgets available on the high street
here in the UK to record a phone conversation. They cost little and
provide an audio feed from a jack plug which can go straight into a
basic voice-activated recorder. Simple. Cheap.

So if I actually wanted to record a phone line I would use something
like that. Perfectly legal too.


However I have asked about something different. I want to switch an
electrical device on when the landline is in use. My question is how
to attach to the landline. Something non-invasive is better and I
suggested a magnetic switch. If it has to be a plug-in device then
that's ok although it limits the location of the point of attachment
to only where the sockets are.

 

[John Larkin]

On Wed, 06 Jun 2007 11:25:25 -0700, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

John Larkin wrote:

On Wed, 06 Jun 2007 00:59:39 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:


Hello Folks,

Ok, first, those card ejectors from RichCo and other mfgs don't seem to
be in stock anywhere. Is there a place that sells them by the dozens and
not truck loads?

Other: We've designed the boards per spec. Holes for the ejector 250mils
in, boards exactly Eurocard length (160mm) but the boards aren't flush
with the front rails of the VME cage. So maybe those ejectors wouldn't
work anyhow.

Are there any "pull tools" available? We used to have those for
ultrasound machines because ejectors were rattling to much. But that was
many moons ago and I don't have the foggiest where they came from.
Basically they caught the holes and then you cantilevered the board out.
Of course, engineers didn't want to be sissies so we kept pulling by
hand until thick callusses developed.


We use the Schroff ejectors. The classic eurocard stops about 0.1" shy
of the back of the front panel, but sometimes we cheat and close the
gap to almost zero, for various reasons.

Did I send you my board layout? I forget. If you're using my dims, I
could send you a few Schroff ejectors and a panel to try, and a
solder-sample bare board, just for fun. Heck, I could just send you a
whole VME module.


Yes, I've got your CAD file.


Hmmm... our standard board (the standard setback one) is 160 mm wide,
with the ejector hole 140 mils in from the front edge of the board.


Ah, that's why. We had used the dims from the Interfacebus web site for
the ejectors because they were somewhat of an "afterthought". So I guess
we won't be able to use ejectors :-(


Our longer board, the one that hits the rear of the front panel, is
6.400" wide, 162.56 mm, and the ejector hole is 240 mils from the
board edge.


And we used 240mils on the ones that didn't hit the panel. Sigh...

It's a 115 drill, so you could re-drill it 100 mils closer to the
front. The ugly figure-8 hole would be mostly hidden under the
extractor. Might work.

Hey, we're getting together a box full of old boards to go the the
dump. Want any?

John

 

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[Joerg]

Hello,

Just curious, although I am not holding my breath that any exist:

Are there FETs with a Vds rating of 300V or higher, preferably DPAK
(TO-252), that have a guaranteed Rdson of around 1ohm or less at Vgs of
6V or less? 1A current or higher.

With guaranteed I mean not in some graph but with an entry under "max"
in the tables. The usual ones are only rated at 10V although the figures
indicate that they could have rated them for lower gate drive voltages
at lesser current. But the manufacturers chose not to and trying to get
any endorsement to that effect is like kicking a big oak tree.

The motivation is the usual. Logic drive, the typical MIC4422 or similar
is too much money plus it would need its personal supply voltage which
would have to be made.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

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