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You also have to worry about the extrinsic base resistance, Rbb'. I use
a lot of 2SD2704K's for cap multipliers of about that power level, but
they only come in SOT23. AOE3 lists a bunch of low noise BJTs on P.
501. You might look at the ZXT851, which is a fave of theirs.
Yeah, So this to-92 pac transistor is also the 'fuse'
if kids pull too much. (there's a ~300 mA current limit up stream.)
George Herold wrote...
Oh I want to say I love all the different ideas!
(I'll look tomorrow at work) Thanks.
George, forget beta and the other parameters.
It's all about r_bb'. That's hard to measure,
except through noise measurements, which is
why we did for you. We were not impressed
with the 2n4401 series for low noise.
George Herold wrote...
Hey, did you ever measure the TIP31/32? I use that in another
low noise supply, and it's nice... Well that supply has a
quieter voltage reference feeding the C-mult so that helps.
Following rumors found on audio DIY forums, we
measured a number of power types. Some weren't
very bad, but they varied greatly from part to
part. Two power parts made it onto our table,
in good spots: BD437 TO-126 and BU406 TO-220,
but awwkk, they have horrible measured beta.
So instead I suggest a Sziklai power stage.
--
Thanks,
- Win
On 2019-05-24, George Herold <gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 5:18:43 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:30:41 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
Way overkill.
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
That makes no current in the transistor.
Oh dear, The Vref is to gnd. I could float things on the input end.
I'll have to try it now.. well tomorrow.
https://www.dropbox.com/s/3tlaygyv0xwixxp/Beta.JPG?dl=0
I don't want so much voltage drop across the transistor.
100 mA is a lot for the to-92 pac.
use +1V instead of +5, that'd be more representative of the operating
area of a cap multiplier.
On 5/23/19 8:09 PM, George Herold wrote:
On Thursday, May 23, 2019 at 5:12:13 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:01:16 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Low beta will make higher Ib, and Ib has shot noise. Ib noise makes
voltage noise in whatever impedance the base sees. I guess Ib never
makes it to the collector, either.
Internal base resistance Rbb directly makes Johnson voltage noise, and
Rbb could vary a lot in random generic 2N4401s. See Win's chart on p
501 of AoE3. My favorite gumdrop, BCX70, is the worst in his list with
Rb of 760 ohms. That makes about 3.6 nV/rtHz, but doesn't matter if
I'm just turning LEDs or relays on and off.
2N4401 is in Win's table, at 40 ohms Rbb. But your transistors might
have come from anywhere. ZTX718 looks good.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
OK, I forgot to say that the noise gets higher with temperature.
(current) I test 'em with 100 ohm Al body power R's 25W.
The power R's sit in the same shielded box with the front end
opamps and gain R's.
The ~2 watts of power heats everyone up...
guess what, the 'amplifier noise' goes up too. :^)
Driving home I was thinking I should just change the noise spec.
in the manual/ website. And send some newsletter/ circuit, showing how
to measure the power supply noise... then that can go into your
calc. of the total noise. It mostly 'could' only matter when driving
the incandescent light bulb... and then at the highest currents vibration
noise in the bulb filament overwhelms the power supply noise.
(at some frequencies :^)
Noise is fun...
George H.
The thing that hacks me off is the photodiode equivalent of Rbb', i.e.
the sheet resistance of the epi layer. Your average 0.1-inch square
photodiode has about 60 ohms' series resistance, and some are much
worse. (I'm looking at you, Vishay.)
That noise gets differentiated by the diode capacitance just like the
TIA's input noise voltage, and is often the limiting factor in low-light
measurements.
Cheers
Phil Hobbs
On 5/23/19 4:30 PM, George Herold wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
You also have to worry about the extrinsic base resistance, Rbb'. I use
a lot of 2SD2704K's for cap multipliers of about that power level, but
they only come in SOT23. AOE3 lists a bunch of low noise BJTs on P.
501. You might look at the ZXT851, which is a fave of theirs.
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 Fri, 24 May 2019 03:14:48 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
On 5/23/19 8:09 PM, George Herold wrote:
On Thursday, May 23, 2019 at 5:12:13 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:01:16 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Low beta will make higher Ib, and Ib has shot noise. Ib noise makes
voltage noise in whatever impedance the base sees. I guess Ib never
makes it to the collector, either.
Internal base resistance Rbb directly makes Johnson voltage noise, and
Rbb could vary a lot in random generic 2N4401s. See Win's chart on p
501 of AoE3. My favorite gumdrop, BCX70, is the worst in his list with
Rb of 760 ohms. That makes about 3.6 nV/rtHz, but doesn't matter if
I'm just turning LEDs or relays on and off.
2N4401 is in Win's table, at 40 ohms Rbb. But your transistors might
have come from anywhere. ZTX718 looks good.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
OK, I forgot to say that the noise gets higher with temperature.
(current) I test 'em with 100 ohm Al body power R's 25W.
The power R's sit in the same shielded box with the front end
opamps and gain R's.
The ~2 watts of power heats everyone up...
guess what, the 'amplifier noise' goes up too. :^)
Driving home I was thinking I should just change the noise spec.
in the manual/ website. And send some newsletter/ circuit, showing how
to measure the power supply noise... then that can go into your
calc. of the total noise. It mostly 'could' only matter when driving
the incandescent light bulb... and then at the highest currents vibration
noise in the bulb filament overwhelms the power supply noise.
(at some frequencies :^)
Noise is fun...
George H.
The thing that hacks me off is the photodiode equivalent of Rbb', i.e.
the sheet resistance of the epi layer. Your average 0.1-inch square
photodiode has about 60 ohms' series resistance, and some are much
worse. (I'm looking at you, Vishay.)
That noise gets differentiated by the diode capacitance just like the
TIA's input noise voltage, and is often the limiting factor in low-light
measurements.
Cheers
Phil Hobbs
Does anyone add some surface conductors, like a solar cell?
On Thu, 23 May 2019 13:30:41 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
Way overkill.
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
That makes no current in the transistor.
https://www.dropbox.com/s/3tlaygyv0xwixxp/Beta.JPG?dl=0
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
On Thursday, May 23, 2019 at 5:18:43 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:30:41 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
Way overkill.
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
That makes no current in the transistor.
https://www.dropbox.com/s/3tlaygyv0xwixxp/Beta.JPG?dl=0
Friday closure. I measured beta of a few of the transistors (1,10,100 mA)
(using JL's circuit above, collector grounded) and found no correlation
between beta and the noise. Only a few data points, but the noisest 2n4401
had a higher beta, than a quite one...
On Thursday, May 23, 2019 at 5:18:43 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:30:41 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
Way overkill.
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
That makes no current in the transistor.
https://www.dropbox.com/s/3tlaygyv0xwixxp/Beta.JPG?dl=0
Friday closure. I measured beta of a few of the transistors (1,10,100 mA)
(using JL's circuit above, collector grounded) and found no correlation
between beta and the noise. Only a few data points, but the noisest 2n4401
had a higher beta, than a quite one...
George H.
 I measured beta of a few of the transistors (1,10,100 mA)
(using JL's circuit above, collector grounded) and found no correlation
between beta and the noise. Â
Ahh, OK. I've got these wired in to my white proto board.On Fri, 24 May 2019 13:42:54 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 5:18:43 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:30:41 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
Way overkill.
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
That makes no current in the transistor.
https://www.dropbox.com/s/3tlaygyv0xwixxp/Beta.JPG?dl=0
Friday closure. I measured beta of a few of the transistors (1,10,100 mA)
(using JL's circuit above, collector grounded) and found no correlation
between beta and the noise. Only a few data points, but the noisest 2n4401
had a higher beta, than a quite one...
George H.
Probably base resistance, Rbb. It would be interesting to check b-e
with a DVM on the ohms or diode range, and see how that correlates to
noise.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Low beta will make higher Ib, and Ib has shot noise. Ib noise makes
voltage noise in whatever impedance the base sees. I guess Ib never
makes it to the collector, either.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
Couldn't you do a current/voltage graph of the b-e
junction and figure out Rbb from that? Would the
ohmic part of the curve be Rbb?
Win,
could you recommend transistors for Sziklai
power stage for ~450mA-500mA cap mult?
On Friday, May 24, 2019 at 6:02:46 PM UTC-4, John Larkin wrote:
On Fri, 24 May 2019 13:42:54 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 5:18:43 PM UTC-4, John Larkin wrote:
On Thu, 23 May 2019 13:30:41 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:
On Thursday, May 23, 2019 at 4:01:25 PM UTC-4, George Herold wrote:
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
Way overkill.
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
Something like this?
https://www.dropbox.com/s/ozao49go305ik8q/Beta.JPG?dl=0
GH
That makes no current in the transistor.
https://www.dropbox.com/s/3tlaygyv0xwixxp/Beta.JPG?dl=0
Friday closure. I measured beta of a few of the transistors (1,10,100 mA)
(using JL's circuit above, collector grounded) and found no correlation
between beta and the noise. Only a few data points, but the noisest 2n4401
had a higher beta, than a quite one...
George H.
Probably base resistance, Rbb. It would be interesting to check b-e
with a DVM on the ohms or diode range, and see how that correlates to
noise.
Ahh, OK. I've got these wired in to my white proto board.
(I looked at the emitter voltage with a scope and saw no bad
oscillations.) You want me to check V_be. I can do that,
but you have to wait till Tuesday! (My kids have voted for
shiskaba..(I don't know how to spell that word.) ...
... Chicken,
beef, onions, peppers, tomatoes, stuck on a stick and marinated
in Chiavetta's (I was going to say you can't get any... but
amazon.),
https://www.amazon.com/Buffalos-Own-Chiavettas-Barbecue-Marinade/dp/B0058ORTXY?th=1
It's heavy vinegar and I like to add some tomato sauce and
honey.
What's the best beef for shiskaba?
Hi all, We make this low noise power supply. (~ +/- 12V up to ~100mA)
A voltage regulator followed by a cap-multiplier. The first bunch I made had an output noise of ~>1.5 nV/rtHz.
So I wrote a spec of 2nV/rtHz. Then a new batch of transistors (2N4401)
and the noise was worse... ~3.5 nV/rtHz. I had a bag of the older npn's
and just put those in. Now I've run low and ordered a bunch of them (200)
from several different suppliers. These are in now and some of them
test just fine. (transistors from the same batch seem to be very similar)
And I was wondering if the difference in noise is related to a difference in
Beta. (Can I do a DC measurement and ID the good ones?) So I'm looking for
a simple circuit to measure transistor beta. This looks like a good
start,
https://electronicsarea.com/circuit-measuring-beta-of-transistor/
The noise is highest at the highest currents, so I'd like the current source
to ~100 mA. I guess that's simple enough.
Other ideas? Thoughts? Thanks.
George H.
I'd use a high-beta, low r'bb part like
an NPN ZTX618 or FMMT618. Run it at 20mA
with a 33-ohm PNP base-emitter resistor,
and a PNP power transistor of your choice.