Composite amps

On Sun, 22 Mar 2020 02:17:10 -0700 (PDT), plastcontrol.ru@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 1.23ľA
http://ixbt.photo/?id=photo:1332242

output signal from OPA656 with photocurrent 1.23ľA
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

 

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@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]

On 2020-05-03 15:00, plastcontrol.ru@gmail.com wrote:

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