On Thursday, 27 February 2020 19:20:03 UTC, plastco...@gmail.com wrote:> For gas sensor : > 4 keV / 30 = 133ē > For scintillator - SiPM ! > > http://ixbt.photo/?id=photo:1330019eh?
Composite amps
Started by ●May 27, 2018
Reply by ●February 27, 20202020-02-27
Reply by ●February 27, 20202020-02-27
Best result OPA140+BF862 (L=1mH+1mH drain load): http://ixbt.photo/?id=photo:1329969 Rf=91k and Rf=1M http://ixbt.photo/?id=photo:1330021 Pushmi-Pullyu dual accelerator - input JFET, output pnp BJT DC precision power supply +-3.8V active probe - bootstrapped dual JFET half-bridge CPH6904 (out=in+0.86V) (mediocre, better jfet+ADA4860 or FVF (Flipped Voltage Follower) with BF998) http://ixbt.photo/?id=photo:1330027 Tortoise outrun Achilles ! time: 1.25us Сircuit speed indifferent to input capacitance ! http://ixbt.photo/?id=photo:1330025 Сheetah enters the arena: http://ixbt.photo/?id=photo:1330022 only 1M + 2200pF + OPA656 poor substitute, OPA140+jfet better The final, a curtain. OPA656 + BF862 http://ixbt.photo/?id=photo:1330023 GBW=31 GHz ? ((
Reply by ●February 27, 20202020-02-27
On Thursday, February 27, 2020 at 6:10:34 PM UTC-5, plastco...@gmail.com wrote:> Best result OPA140+BF862 (L=1mH+1mH drain load): > http://ixbt.photo/?id=photo:1329969I'm confused about the two traces are here. The BF862 is unfortunately no more... You can only surf so long on the trailing edge of technology.> > Rf=91k and Rf=1M > http://ixbt.photo/?id=photo:1330021Is this for me? Hard to tell the shape of the response for the 91k. But the 1M looks more like a two pole response now anyway.> > Pushmi-Pullyu > dual accelerator - input JFET, output pnp BJT > DC precision > power supply +-3.8V > active probe - bootstrapped dual JFET half-bridge CPH6904 (out=in+0.86V) > (mediocre, better jfet+ADA4860 or FVF (Flipped Voltage Follower) with BF998) > http://ixbt.photo/?id=photo:1330027So all the stuff on the left is an active probe? To look at the inverting node without loading down with capacitance? So is this right? The jfet is taking the fast part of the current signal and sending it through to the non-inverting input? I don't know what the pnp is doing on the output. Unless it's a driver for some coax cable output? It looks the the 'output' (your arrow between collector of pnp and 1k R to -V) should be near -V... are you now biasing PD via the output?> > Tortoise outrun Achilles ! > time: 1.25us > Сircuit speed indifferent to input capacitance ! > http://ixbt.photo/?id=photo:1330025Well at least to C on the inverting node.> > Сheetah enters the arena: > http://ixbt.photo/?id=photo:1330022 > only 1M + 2200pF + OPA656 > poor substitute, OPA140+jfet better > > The final, a curtain. > OPA656 + BF862 > http://ixbt.photo/?id=photo:1330023 > GBW=31 GHz ? ((Huh the opa656 looks nice.. +/- 5V. Thanks Have you been lurking here long... I'm just reminded of Jan Pantelje (sp) Which is a good thing. I like Jan. George H.
Reply by ●February 28, 20202020-02-28
> Rf=91k and Rf=1M > http://ixbt.photo/?id=photo:1330021 >Is this for me? Hard to tell the shape of the response >for the 91k. But the 1M looks more like a two pole response >now anyway.With Rf=91k now Cf>0pF must be present> > Pushmi-Pullyu > dual accelerator - input JFET, output pnp BJT > DC precision > power supply +-3.8V > active probe - bootstrapped dual JFET half-bridge CPH6904 (out=in+0.86V) > (mediocre, better jfet+ADA4860 or FVF (Flipped Voltage Follower) with BF998) > http://ixbt.photo/?id=photo:1330027>So all the stuff on the left is an active probe? >To look at the inverting node without loading down with capacitance?Yes, the circuit is very sensitive to the probe capacitance. Non-inverting node !>So is this right? The jfet is taking the fast part of the >current signal and sending it through to the non-inverting input?JFET is input AC amplifier with feedback through Op Amp TIA))>I don't know what the pnp is doing on the output. Unless >it's a driver for some coax cable output? >It looks the the 'output' (your arrow between collector >of pnp and 1k R to -V) should be near -V... are you >now biasing PD via the output?MMBTH81 is amplifier with gain~10 look in the upper right corner of the book AoE)) no photodiode offset ! slew rate only doubles(( overall gain increases Capacitance SiPM 60035 = 3400pF Dmitriy P.
Reply by ●February 28, 20202020-02-28
On Friday, 28 February 2020 00:44:11 UTC, George Herold wrote:> On Thursday, February 27, 2020 at 6:10:34 PM UTC-5, plastco...@gmail.com wrote:> > Best result OPA140+BF862 (L=1mH+1mH drain load): > > http://ixbt.photo/?id=photo:1329969> I'm confused about the two traces are here. > The BF862 is unfortunately no more... > You can only surf so long on the trailing edge of technology.Russia is expert at that game. NT
Reply by ●February 28, 20202020-02-28
On 2020-02-26 21:18, jlarkin@highlandsniptechnology.com wrote:> On Wed, 26 Feb 2020 16:57:25 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2020-02-26 13:36, George Herold wrote: >>> On Monday, February 24, 2020 at 2:47:45 PM UTC-5, Phil Hobbs wrote: >>>> On 2020-02-24 11:47, George Herold wrote: >>>>> On Monday, February 24, 2020 at 6:55:54 AM UTC-5, plastco...@gmail.com wrote: >>>>>> 1) grounded detector, grounded source/emitter HF transistor >>>>>> 2) true zero-bias operation of detector >>>>>> 3) my circuit is simpler >>>>>> I like to read books)) >>>>> >>>>> OK, what do you find better about zero bias operation? >>>>> I should admit that for many years I ran all my PD's at >>>>> zero bias. I thought this gave me better 'zero' light detection. >>>>> (No DC offset with no light... but the dark current from >>>>> PDs is generally pretty low.) >>>>> Running with some bias has two main advantages. >>>>> 1.) reduced C.. faster >>>>> 2.) Higher saturation current (light intensity) without bias the >>>>> electrons build up in the junction and it saturates.. more light >>>>> gives no more electrons. >>>>> >>>>> George H. >>>>> (who is addicted to reading... I need to find a few new fiction writers) >>>>> >>>> >>>> Zero bias is better in one respect: you can get zero leakage current. >>>> For jobs such as very wide range, very slow photometers, that's a win. >>>> Garry Epeldauer et al. wrote a beautiful paper about getting 14 orders >>>> of magnitude in photocurrent, if you don't mind being stuck with >>>> millihertz bandwidths: >>>> >>>> <https://electrooptical.net/www/optics/eppeldauer14decadephotocurrent.pdf> >>> Hi Phil, I downloaded the above and was chewing through it last night. >>> Great stuff! >>> 1.) Rs (PD shunt resistance... I've always just treated this as >>> infinite. Can I measure leakage current and get Rs? >>> 2.) pg 3094 has a nice discussion of 1/f noise. >>> 3.) Are there even better low current opamps these days? >>> 4.) Nice effective BW calcs in App A. >>> I would add to that, the ENBW for a two pole filter, f_3dB and Q, >>> is >>> ENBW = f_3dB * Q *pi/2 = ~1.11 f_3dB (Q=0.707.. Butterworth) >>> >> >> Re: noise BW >> Yeah, it's like 1.22x for two noninteracting RC poles, so 1.11 for >> Butterworth sounds roughly right. >> >> Re: shunt resistance >> >> For bias voltages << kT/e, both the forward and reverse diffusion >> currents are contributing to the conductance--it's just dI/dV, and so is >> fairly far from zero for a large-area diode run at zero bias. >> >> Ideally the effective shunt resistance goes up by a factor of 2 or so >> with 50 mV of reverse bias, because you shut off the reverse diffusion >> current without introducing significant additional leakage. That's a >> super useful trick with InGaAs diodes in dim light. >> >> re: 1/f noise >> Haven't read it recently, but in photodiodes you actually can get >> significant 1/f noise at zero bias, unlike in the case of resistors. >> >> re: low current op amps >> >> BITD I used to really like the OPA111. Its performance was easy to >> remember: 1 MHz bandwidth, 1 mV offset, 1 uV/K drift, 1 pA input bias. >> (See? I haven't used one in 30 years and I still remember.) ;) >> >> It was one of the primo op amps used in early tunnelling and atomic >> force microscopy. Of course it's noisy, but not nearly as bad as the >> other popular super-high-Z op amp of the day, namely the LM11. >> >> Nowadays there are much better choices, e.g. JL's fave OPA197. >> >> Cheers >> >> Phil Hobbs > > I don't use that as a low noise high-performance amp, but as a > general-purpose gumdrop. It's stable with a big output cap, 3.3u film > or 100u polymer.I didn't mean that you thought it was the best one, but it's sure better than an OPA111. ;) I'm also partial to the OPA140, which is just about the perfect JFET op amp: 0.5 pA typical Ibias at 25C, 5 nV 1-Hz flatband noise, 30 Hz 1/f corner, 11 MHz BW, 220 uV max offset over temperature, 0.25 uV/K typical drift, $2. Not horrible at all. 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
Reply by ●February 29, 20202020-02-29
I remembered where the zero offset of the photodiodes is still important ! Excellent mid-infrared photodiodes from Russia - http://www.mirdog.spb.ru/products.htm Ro = 5 Ω ... 10 k Dmitriy P.
Reply by ●February 29, 20202020-02-29
On Friday, February 28, 2020 at 2:15:33 AM UTC-5, plastco...@gmail.com wrote:> > Rf=91k and Rf=1M > > http://ixbt.photo/?id=photo:1330021 > >Is this for me? Hard to tell the shape of the response > >for the 91k. But the 1M looks more like a two pole response > >now anyway. > With Rf=91k now Cf>0pF must be present > > > > > Pushmi-Pullyu > > dual accelerator - input JFET, output pnp BJT > > DC precision > > power supply +-3.8V > > active probe - bootstrapped dual JFET half-bridge CPH6904 (out=in+0.86V) > > (mediocre, better jfet+ADA4860 or FVF (Flipped Voltage Follower) with BF998) > > http://ixbt.photo/?id=photo:1330027 > > >So all the stuff on the left is an active probe? > >To look at the inverting node without loading down with capacitance? > Yes, the circuit is very sensitive to the probe capacitance. > Non-inverting node ! > > >So is this right? The jfet is taking the fast part of the > >current signal and sending it through to the non-inverting input? > JFET is input AC amplifier with feedback through Op Amp TIA)) > > >I don't know what the pnp is doing on the output. Unless > >it's a driver for some coax cable output? > >It looks the the 'output' (your arrow between collector > >of pnp and 1k R to -V) should be near -V... are you > >now biasing PD via the output? > MMBTH81 is amplifier with gain~10 > look in the upper right corner of the book AoE)) > no photodiode offset ! > slew rate only doubles(( > overall gain increasesOK got it, thanks. I'm so-so at single transistor design. George H.> > Capacitance SiPM 60035 = 3400pF > Dmitriy P.
Reply by ●March 7, 20202020-03-07
Composite voltage follower CFA ADA4860 + BF862 http://ixbt.photo/?id=photo:1330880 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
Reply by ●March 7, 20202020-03-07
On Saturday, March 7, 2020 at 3:15:17 AM UTC-5, plastco...@gmail.com wrote:> Composite voltage follower > CFA ADA4860 + BF862 > http://ixbt.photo/?id=photo:1330880Huh? 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.> > 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
