On Mon, 24 Feb 2020 15:46:09 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2020-02-24 15:13, John Larkin wrote: >> On Mon, 24 Feb 2020 14:47:33 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> 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> >>> >>> Crappy PN photodiodes and solar cells don't respond well to large >>> reverse bias either. >>> >>> For just about anything else, zero bias is a complete crock. >>> >>> With almost any PIN diode, APD, MPPC, (etc) zero bias is a disaster. >>> Applying reverse bias to a PIN diode can reduce its capacitance by a >>> factor of 7 or so, which reduces the high frequency noise by the same >>> factor. >>> >>> Cheers >>> >>> Phil Hobbs >> >> I know of a large organization that has wasted about a million dollars >> a year, since 2002, by running a lot of very expensive Hamamatsu >> photodiodes at zero bias. >> >> https://www.dropbox.com/s/wm3a3cpxa8tcarg/S8551_1.JPG?raw=1 >> >I suspect I know the organization. ;) >They have some very good folks though. > >Cheers > >Phil HobbsPrice's law. They have a few brilliant people and an army of duds. But if the brilliant people retire, or otherwise go away, it might take a while for the world to notice. IBM, Xerox, Kodak, Polaroid, Boeing, Motorola, RCA, DEC, Nokia. -- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
Composite amps
Started by ●May 27, 2018
Reply by ●February 24, 20202020-02-24
Reply by ●February 25, 20202020-02-25
Photodiodes from Russia for similar applications - http://www.technoexan.ru/pdf/silicon_detector/spd100uv.pdf https://www.researchgate.net/publication/266227378_Silicon_precision_detectors_for_near_IR_visible_UV_XUV_and_soft_X-ray_spectral_range price less than $300 http://ixbt.photo/?id=photo:1183963 Quantum noise from fatty X-ray photons is much larger than the shot noise of the dark current at the same value))
Reply by ●February 25, 20202020-02-25
On 2020-02-25 01:46, plastcontrol.ru@gmail.com wrote:> Photodiodes from Russia for similar applications - > http://www.technoexan.ru/pdf/silicon_detector/spd100uv.pdf > https://www.researchgate.net/publication/266227378_Silicon_precision_detectors_for_near_IR_visible_UV_XUV_and_soft_X-ray_spectral_range > price less than $300 > http://ixbt.photo/?id=photo:1183963 > Quantum noise from fatty X-ray photons is much larger than the shot noise of the dark current at the same value)) >$300 for a garden variety PN photodiode? Nice work if you can get it. You can get an MPPC that size with a gain of a million for about the same money. 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 25, 20202020-02-25
On Tuesday, February 25, 2020 at 1:46:20 AM UTC-5, plastco...@gmail.com wrote:> Photodiodes from Russia for similar applications - > http://www.technoexan.ru/pdf/silicon_detector/spd100uv.pdf > https://www.researchgate.net/publication/266227378_Silicon_precision_detectors_for_near_IR_visible_UV_XUV_and_soft_X-ray_spectral_range > price less than $300 > http://ixbt.photo/?id=photo:1183963 > Quantum noise from fatty X-ray photons is much larger than the shot noise of the dark current at the same value))Seems spendy, I think the big PD's from osi-optoelectronics are ~$50. The extra noise from x-rays is easy to understand. Each x-ray is going to come in and make a number of e-h pairs. (let's say on average there are ten electrons made per photon.) So the 'pieces' of charge causing the noise are ten times bigger and you get ten times the noise density. George H.
Reply by ●February 25, 20202020-02-25
On Tuesday, February 25, 2020 at 7:40:26 AM UTC-5, Phil Hobbs wrote:> On 2020-02-25 01:46, plastcontrol.ru@gmail.com wrote: > > Photodiodes from Russia for similar applications - > > http://www.technoexan.ru/pdf/silicon_detector/spd100uv.pdf > > https://www.researchgate.net/publication/266227378_Silicon_precision_detectors_for_near_IR_visible_UV_XUV_and_soft_X-ray_spectral_range > > price less than $300 > > http://ixbt.photo/?id=photo:1183963 > > Quantum noise from fatty X-ray photons is much larger than the shot noise of the dark current at the same value)) > > > $300 for a garden variety PN photodiode? Nice work if you can get it. > You can get an MPPC that size with a gain of a million for about the > same money. > > 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.comYears back I bought PD's from advanced-photonix (I think they had a different name to start.. bought out or something.) Then the prices more than doubled and I went elsewhere. They still seem to be in business. https://www.digikey.com/product-detail/en/advanced-photonix/290-12-22-241/209-290-12-22-241-ND/1012520 George H.
Reply by ●February 25, 20202020-02-25
Russian photodiode for 13 nm, is expensive. Example: 4keV photon, 4000/3.6 ~1100e, square root = 33 quantum noise 33 times greater than dark current Demo version e-PHEMT 40-140 mA (or SiGe BFU910F 2mA) boosted TIA : http://ixbt.photo/?id=photo:1329848 Gate current ATF-53189 ~85nA
Reply by ●February 25, 20202020-02-25
On 2020-02-25 14:13, plastcontrol.ru@gmail.com wrote:> Russian photodiode for 13 nm, is expensive. > Example: 4keV photon, 4000/3.6 ~1100e, square root = 33 > quantum noise 33 times greater than dark current > > Demo version e-PHEMT 40-140 mA (or SiGe BFU910F 2mA) boosted TIA : > http://ixbt.photo/?id=photo:1329848 > > Gate current ATF-53189 ~85nA >That's sort of silly, because it relies on the OPA140 to complete the loop, and that grossly limits the speed. You can do a _lot_ better than 2 us rise time (massively underdamped) with 2200 pF. It works a lot better if you run the pHEMT as a follower and return the anode of the PD to the pHEMT source via a capacitor. You'll need a good ferrite bead in the gate to prevent oscillation--try a BLM18BA100SN1. The ATF53189 is obsolete, like all the 3-GHz HP/Avago/Broadcom pHEMTs. A gizmo of mine that works that way is at <https://electrooptical.net/News/silicon-photomultiplier-sipm-mppc-system-for-cathodoluminescence/>. The detector capacitance is between 350 and 1400 pF, so the comparison is reasonable. If you used a PIN diode and reverse biased it, you'd be around 100 pF rather than 8 nF for that 1 cm**2 device. That would get you a noise reduction of about 38 dB essentially free. That sort of improvement matters to some of us. ;) Of course it might or might not work with X-rays. 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 25, 20202020-02-25
> >It works a lot better if you run the pHEMT as a follower and return the >anode of the PD to the pHEMT source via a capacitor. >IMHO, the follower or my wiring diagram does not make any difference - only the location of the symbol GND ! From the point of view of the photodiode, one circuit pulls on the lower terminal, the other circuit operates on the upper pin. All properties are similar. My JFET BF862 is installed more conveniently - single-supply compatible. It is very interesting to observe the voltage at the input of the amplifier. http://ixbt.photo/?id=album:30781 Why no one broke the taboo - disconnect the non-inverting input Op Amp from GND ?
Reply by ●February 25, 20202020-02-25
On Tuesday, February 25, 2020 at 2:13:52 PM UTC-5, plastco...@gmail.com wrote:> Russian photodiode for 13 nm, is expensive.OK sure... just run with no window?> Example: 4keV photon, 4000/3.6 ~1100e, square root = 33 > quantum noise 33 times greater than dark currentYeah, I know little of x-rays. Is the depth of the depletion region such that the x-ray loses all it's energy there? You could use the noise to measure the QE of the detector. (If you knew the energy.) (maybe you already do that.) (or measure x-ray energy from the noise.. OK that's probably a silly idea.. easier to measure x-ray energy from a pulse height or total current or something.)> > Demo version e-PHEMT 40-140 mA (or SiGe BFU910F 2mA) boosted TIA : > http://ixbt.photo/?id=photo:1329848 > > Gate current ATF-53189 ~85nAOK that's fun. Dmitriy, (SED's own Russian troll* :^) 2 us rise time with 1 meg and 2200pF is nice. With a smaller PD and both bootstrap and cascode I think I got about a 1 us rise time. (Phil and Win do better.) (I had slower opamp and transitors.. ) Is the yellow trace, chan. 1, the output? That looks mostly like a single pole. Which means (to me) that there is a single capacitance slowing things down. It could be C in parallel with the 1 meg FB resistor. (what does step response with 100k ohms look like?) If not that you should consider setting aside an afternoon to try biasing the PD. Have you read the TIA section in AoE3? (Win's book) George H. *I say that lovingly.
Reply by ●February 25, 20202020-02-25
On Tuesday, February 25, 2020 at 4:06:42 PM UTC-5, plastco...@gmail.com wrote:> > > >It works a lot better if you run the pHEMT as a follower and return the > >anode of the PD to the pHEMT source via a capacitor. > > > > IMHO, the follower or my wiring diagram does not make any difference - only the location of the symbol GND ! > From the point of view of the photodiode, one circuit pulls on the lower terminal, the other circuit operates on the upper pin. > All properties are similar. > My JFET BF862 is installed more conveniently - single-supply compatible. > It is very interesting to observe the voltage at the input of the amplifier. > > http://ixbt.photo/?id=album:30781 > > Why no one broke the taboo - disconnect the non-inverting input Op Amp from GND ?OK the layout of the circuit is of utmost importance. You could post a pic or something. You do realize that you've biased the photodiode by 1/2 your supply voltage. (Doesn't that also bias your DC output?.. checks trace, right ~1.3 volts below ground.) I've seen other schematics that bias the opamp rather than the photodiode. I've never liked them because I like DC =0 at zero light. Better for me is a lop-sided supply for the opamp. (and bias the PD more. At least 10V unless the manufacturer says not to.) George H.
