C-multipliers and simple circuit to measure npn beta.

[George Herold]

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.

 

[George Herold]

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

 

[John Larkin]

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

 

[John Larkin]

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

 

[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

 

[Joerg]

On 2019-05-23 13:01, 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.

This should be simpler:

https://en.wikipedia.org/wiki/Current_source#/media/File:Const_cur_src_111.svg

Set the current to 100mA and hang a meter into the base connection, set
to current measurement. For example, one of the $5 Harborfreight
multimeters.

Running these at 100mA in linear mode is "pedal to the metal".

--
Regards, Joerg

http://www.analogconsultants.com/

 

[LM]

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.

It is easiest just to buy a cheap DVM which can measure betas.
But there is a quick and simple way, two resistors, a battery, ohms
law about currents and a DVM.
Choose resistors so that you get suitable voltages.
Version 4
SHEET 1 880 680
WIRE 272 16 144 16
WIRE 368 16 272 16
WIRE 144 48 144 16
WIRE 272 48 272 16
WIRE 368 96 368 16
WIRE 272 192 272 128
WIRE 144 240 144 128
WIRE 208 240 144 240
WIRE 272 304 272 288
WIRE 368 304 368 176
WIRE 368 304 272 304
WIRE 272 336 272 304
FLAG 272 336 0
SYMBOL res 128 32 R0
SYMATTR InstName R1
SYMATTR Value 1000000
SYMBOL res 256 32 R0
SYMATTR InstName R2
SYMATTR Value 1000
SYMBOL npn 208 192 R0
SYMATTR InstName Q1
SYMBOL voltage 368 80 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9V

 

[Bill Sloman]

On Friday, May 24, 2019 at 7:12:13 AM UTC+10, 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.

Wideband transistors have low base resistance. In normal use use you stick a 27R resistor close to the base to stop them oscillating, but the right inductor might do the job.

--
Bill Sloman, Sydney

 

[George Herold]

On Thursday, May 23, 2019 at 5:35:41 PM UTC-4, Phil Hobbs wrote:

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.

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.)
(You know, I need to think more about protecting the b-e junction.)
We send extra's and they come in phoenix terminal blocks (on the pcb)

George H.

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

 

[George Herold]

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.

George H.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

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.

 

[George Herold]

On Thursday, May 23, 2019 at 5:37:09 PM UTC-4, Joerg wrote:

On 2019-05-23 13:01, 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.


This should be simpler:

https://en.wikipedia.org/wiki/Current_source#/media/File:Const_cur_src_111.svg

Set the current to 100mA and hang a meter into the base connection, set
to current measurement. For example, one of the $5 Harborfreight
multimeters.

Running these at 100mA in linear mode is "pedal to the metal".

In the C-mult. there's not much voltage drop across 'em,
I see some small heating effect, but they are not hot to the touch,
(Even with my lips. :^)

George H.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Winfield Hill]

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.

We found that specific types, from well-known
manufacturers, maintained similar performance,
over decades of production. So pick a part,
and don't change anything. I suggest one of
the Zetez / Diode, Inc. parts from our table.
Then you can give a low noise spec and keep it.


--
Thanks,
- Win

 

[George Herold]

On Thursday, May 23, 2019 at 6:19:42 PM UTC-4, LM 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.


It is easiest just to buy a cheap DVM which can measure betas.
But there is a quick and simple way, two resistors, a battery, ohms
law about currents and a DVM.
Choose resistors so that you get suitable voltages.
Version 4
SHEET 1 880 680
WIRE 272 16 144 16
WIRE 368 16 272 16
WIRE 144 48 144 16
WIRE 272 48 272 16
WIRE 368 96 368 16
WIRE 272 192 272 128
WIRE 144 240 144 128
WIRE 208 240 144 240
WIRE 272 304 272 288
WIRE 368 304 368 176
WIRE 368 304 272 304
WIRE 272 336 272 304
FLAG 272 336 0
SYMBOL res 128 32 R0
SYMATTR InstName R1
SYMATTR Value 1000000
SYMBOL res 256 32 R0
SYMATTR InstName R2
SYMATTR Value 1000
SYMBOL npn 208 192 R0
SYMATTR InstName Q1
SYMBOL voltage 368 80 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 9V

I didn't look at your LTspice circuit. But I want to look at
different collector/emitter currents.. 1-100 mA say.

Oh I want to say I love all the different ideas!
(I'll look tomorrow at work)
Thanks.

George H.

 

[John Larkin]

On Thu, 23 May 2019 17:20:54 -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.
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.

The emitter resistor sets the current. I didn't put a value on that
because I didn't know the desired operating point.

The +5 can be anything you like.

The 33R just keeps the transistor from oscillating.



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Jasen Betts]

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.


--
When I tried casting out nines I made a hash of it.

 

[Phil Hobbs]

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

--
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

 

[Winfield Hill]

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

 

[George Herold]

On Thursday, May 23, 2019 at 9:12:51 PM UTC-4, Winfield Hill wrote:

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.

Hi Win, OK thanks... I'll have to buy some others
and test for myself. I will say that the other npn we
had in stock was the 2n3904 (r_bb = 110 ohms),
and it was worse (noise-wise) compared to the 2n4401.
So that's encouraging.

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.

George H.

We found that specific types, from well-known
manufacturers, maintained similar performance,
over decades of production. So pick a part,
and don't change anything. I suggest one of
the Zetez / Diode, Inc. parts from our table.
Then you can give a low noise spec and keep it.


--
Thanks,
- Win

 

[George Herold]

On Friday, May 24, 2019 at 3:14:55 AM UTC-4, Phil Hobbs 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.)

Huh, Well I've never run into that. I hardly know what r_bb is.
(I'm going to re-read sec 8.3 in AoE3...)

George H.

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

--
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