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George Herold
Guest

Sat Mar 07, 2020 8:45 pm   



On Saturday, March 7, 2020 at 3:15:17 AM UTC-5, plastco...@gmail.com wrote:
Quote:
Composite voltage follower
CFA ADA4860 + BF862
http://ixbt.photo/?id=photo:1330880

Huh? scratch scratch. Dmitriy, I have no idea what
you are doing? What is the input? (for one)
You'd have to describe what you are doing if you wanted some
sort of input/ critic/ ideas. Which would most likely come not
from me, I mostly just ask questions.

George H.
Quote:

Output signals
yellow - circuit A
white - circuit B (bootstrapped)
http://ixbt.photo/?id=photo:1330881

Rise time circuit B (bootstrapped)
http://ixbt.photo/?id=photo:1330882



Guest

Sun Mar 08, 2020 8:45 am   



A unity-gain buffer removes the photodiode's parasitic capacitance :
circuit A - 2200pF >> 15pF
circuit B - 2200pF >> 0.8pF
Bootstrap photodiodes known since 1984, may have been used before.
The operation of the circuit "A" is limited by the capacitance gate-drain of the JFET transistor.


Guest

Sun Mar 15, 2020 12:45 am   



Versatile composite amplifier configuration

https://www.researchgate.net/publication/271747584_Versatile_composite_amplifier_configuration


Guest

Sun Mar 22, 2020 10:45 am   



"Shunt bootstrapping technique to improve bandwidth of transimpedance amplifiers"
https://www.researchgate.net/publication/3380589_Shunt_bootstrapping_technique_to_improve_bandwidth_of_transimpedance_amplifiers

fig.3 Output of bootstrap amplifier

my composite voltage follower -
http://ixbt.photo/?id=photo:1332241

output signal from ADA4860 with photocurrent 1.23µA
http://ixbt.photo/?id=photo:1332242

output signal from OPA656 with photocurrent 1.23µA
http://ixbt.photo/?id=photo:1332243

rise time 70ns, noise 150mVp-p
Channel 2 = output ADA4860

I wish you all good health.


Guest

Sat May 02, 2020 7:45 pm   



Composite amplifier EPHEMT + RGC + OPA656
Cdet=2200pF Rf=1M
ATF-54143 Igate= 18 nA
Bead on gate blm18bb050sn1d
http://ixbt.photo/?id=photo:1339025

Without e-phemt :
http://ixbt.photo/?id=photo:1339026

Rise time :
http://ixbt.photo/?id=photo:1339027
Dmitriy P.


Guest

Sun May 03, 2020 12:45 pm   



Retrospective "composite amplifier" challenge))
Question for experts and authors of the AoE3.
What is the function of capacitors 10nF between base and emitter MMBT6429 ?
https://electronix.ru/forum/uploads/monthly_06_2016/post-21169-1466350930.png
Why is there only one capacitor in the service manual between base and emitter ?
https://electronix.ru/forum/uploads/monthly_06_2016/post-21169-1466350949.png
Dmitriy P.

Winfield Hill
Guest

Sun May 03, 2020 1:45 pm   



plastcontrol.ru_at_gmail.com wrote...
Quote:

Retrospective "composite amplifier" challenge))
Question for experts and authors of the AoE3.
What is the function of capacitors 10nF between base and emitter MMBT6429 ?
https://electronix.ru/forum/uploads/monthly_06_2016/post-21169-1466350930.png
Why is there only one capacitor in the service manual between base and emitter ?
https://electronix.ru/forum/uploads/monthly_06_2016/post-21169-1466350949.png
Dmitriy P.


You're right, my copy of the service manual
only shows one capacitor. The symmetrical
extra one came in, either when I made the
pencil drawing for the draftsman, or they
made a drafting error. As for the purpose
of the capacitors, we can only guess. It'd
be nice to be able to ask the HP engineer(s).

Did we point out in the text that those are
cascode transistors, whose only purpose is to
isolate the op-amp active nodes from the very
high capacitance of the huge IF3602 JFETs?
The Darlington is to insure all of the emitter
current ends up in the collector, and almost
none in the base.

The performance specs for their G=10,000
amplifier are pretty amazing. We have one of
those HP 34420A multimeters in my lab, but
it's rarely used, it's far too good! And the
special nanovolt input connector is awkward.


--
Thanks,
- Win

Michael Terrell
Guest

Sun May 03, 2020 5:45 pm   



On Sunday, May 3, 2020 at 8:09:24 AM UTC-4, Winfield Hill wrote:
Quote:
plastcontrol wrote...

Retrospective "composite amplifier" challenge))
Question for experts and authors of the AoE3.
What is the function of capacitors 10nF between base and emitter MMBT6429 ?
https://electronix.ru/forum/uploads/monthly_06_2016/post-21169-1466350930.png
Why is there only one capacitor in the service manual between base and emitter ?
https://electronix.ru/forum/uploads/monthly_06_2016/post-21169-1466350949.png
Dmitriy P.

You're right, my copy of the service manual
only shows one capacitor. The symmetrical
extra one came in, either when I made the
pencil drawing for the draftsman, or they
made a drafting error. As for the purpose
of the capacitors, we can only guess. It'd
be nice to be able to ask the HP engineer(s).

Did we point out in the text that those are
cascode transistors, whose only purpose is to
isolate the op-amp active nodes from the very
high capacitance of the huge IF3602 JFETs?
The Darlington is to insure all of the emitter
current ends up in the collector, and almost
none in the base.

The performance specs for their G=10,000
amplifier are pretty amazing. We have one of
those HP 34420A multimeters in my lab, but
it's rarely used, it's far too good! And the
special nanovolt input connector is awkward.


Some former HP engineers are on:

https://groups.io/g/HP-Agilent-Keysight-equipment

This replaced the old Yahoo HP group.

Cursitor Doom
Guest

Sun May 03, 2020 5:45 pm   



On Sun, 03 May 2020 09:15:17 -0700, Michael Terrell wrote:

Quote:
Some former HP engineers are on:

https://groups.io/g/HP-Agilent-Keysight-equipment


Yeah, but so is Gardner lately.

Tom Gardner
Guest

Sun May 03, 2020 6:45 pm   



On 03/05/20 17:32, Cursitor Doom wrote:
Quote:
On Sun, 03 May 2020 09:15:17 -0700, Michael Terrell wrote:

Some former HP engineers are on:

https://groups.io/g/HP-Agilent-Keysight-equipment

Yeah, but so is Gardner lately.


Best you stay away.

Or (attempt to) put me in your killfile (again).


Guest

Sun May 03, 2020 6:45 pm   



On Sun, 22 Mar 2020 02:17:10 -0700 (PDT), plastcontrol.ru_at_gmail.com
wrote:

Quote:
"Shunt bootstrapping technique to improve bandwidth of transimpedance amplifiers"
https://www.researchgate.net/publication/3380589_Shunt_bootstrapping_technique_to_improve_bandwidth_of_transimpedance_amplifiers

fig.3 Output of bootstrap amplifier

my composite voltage follower -
http://ixbt.photo/?id=photo:1332241

output signal from ADA4860 with photocurrent 1.23A
http://ixbt.photo/?id=photo:1332242

output signal from OPA656 with photocurrent 1.23A
http://ixbt.photo/?id=photo:1332243

rise time 70ns, noise 150mVp-p
Channel 2 = output ADA4860

I wish you all good health.


I have a new design, a little thing to keep busy with during the
shutdown. It's a GHz o/e converter. The trick is to use both ends of
the photodiode, use the current twice. One end goes into a fast
AC-coupled amp, and one end into a slow, precise DC gain path, and
combine them later.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard


Guest

Sun May 03, 2020 8:45 pm   



воскресенье, 3 мая 2020 г., 19:49:57 UTC+3 пользователь jla...@highlandsniptechnology.com написал:
Quote:
On Sun, 22 Mar 2020 02:17:10 -0700 (PDT), plastcontrol.ru_at_gmail.com
wrote:

"Shunt bootstrapping technique to improve bandwidth of transimpedance amplifiers"
https://www.researchgate.net/publication/3380589_Shunt_bootstrapping_technique_to_improve_bandwidth_of_transimpedance_amplifiers

fig.3 Output of bootstrap amplifier

my composite voltage follower -
http://ixbt.photo/?id=photo:1332241

output signal from ADA4860 with photocurrent 1.23渙
http://ixbt.photo/?id=photo:1332242

output signal from OPA656 with photocurrent 1.23渙
http://ixbt.photo/?id=photo:1332243

rise time 70ns, noise 150mVp-p
Channel 2 = output ADA4860

I wish you all good health.


I have a new design, a little thing to keep busy with during the
shutdown. It's a GHz o/e converter. The trick is to use both ends of
the photodiode, use the current twice. One end goes into a fast
AC-coupled amp, and one end into a slow, precise DC gain path, and
combine them later.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard


It’s interesting to try using still floating power supply op amp.

Dmitriy P.

Phil Hobbs
Guest

Mon May 04, 2020 9:45 pm   



On 2020-05-03 15:00, plastcontrol.ru_at_gmail.com wrote:
Quote:
воскресенье, 3 мая 2020 г., 19:49:57 UTC+3 пользователь
jla...@highlandsniptechnology.com написал:
On Sun, 22 Mar 2020 02:17:10 -0700 (PDT),
plastcontrol.ru_at_gmail.com wrote:

"Shunt bootstrapping technique to improve bandwidth of
transimpedance amplifiers"
https://www.researchgate.net/publication/3380589_Shunt_bootstrapping_technique_to_improve_bandwidth_of_transimpedance_amplifiers





fig.3 Output of bootstrap amplifier

my composite voltage follower -
http://ixbt.photo/?id=photo:1332241

output signal from ADA4860 with photocurrent 1.23渙
http://ixbt.photo/?id=photo:1332242

output signal from OPA656 with photocurrent 1.23渙
http://ixbt.photo/?id=photo:1332243

rise time 70ns, noise 150mVp-p Channel 2 = output ADA4860

I wish you all good health.


I have a new design, a little thing to keep busy with during the
shutdown. It's a GHz o/e converter. The trick is to use both ends
of the photodiode, use the current twice. One end goes into a fast
AC-coupled amp, and one end into a slow, precise DC gain path, and
combine them later.


Using the photocurrent twice is fun, I agree. I sometimes use a cascode
with two collector resistors in series, with a diode clamp on the
higher-value one. You digitize both, and use the lower-gain one when
the high-gain one rails.

That's handy when you have a relatively slow pulsed application where
the signal varies over a wideish range and you don't want to have to do
range switching. I last used it a couple of years ago, in the follow-on
version of my blood spot detector for hen's eggs.

That feedbeside thing is disappointing IME--it settles OK to 1% or so,
but then it's all whoopdedoos. Good for scopes, which is where it was
originally used.

> It’s interesting to try using still floating power supply op amp.

Yup. You do have to watch out for the CMR though--TIAs with
bootstrapped power supplies can lead to oscillations. CMR is
input-referred, and in a TIA the noise gain gets pretty high at high
frequency, just where the CMR is tanking.

It's usually the negative CMR that's the problem.

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

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