Hi, I need some design help! I’ll try to be brief…
My setup are multiple gamma detectors each with a scintillator followed by an MPPC->Amp->ADC. The objective is to measure the time difference between incident gamma photons to the detectors to attain time of flight information (TOF) and thereby determine the position of a radioactive source. The time resolution should be sub-nanoseconds.
The MPPC and ADC is fixed, however I have difficulties designing a working Amplifier.
What I need are Current-to-Voltage amplifier designs with set 20, 50 and 100 times gain and >400MHz BW.
For my application I consider fast rise time and bandwidth as the most crucial requirements, and precision, noise rejection… as secondary since the energy resolution of the scintillators is rather low.
I have experimented using the OPA 847 and OPA 695 op-amps in transimpedance configuration. However I have not succeeded in getting a stable design without using very high gain (Rf=5.6k++) which causes unwanted loss of bandwidth and a too high signal for my +/-1 V range ADC.
The MPPC’s used:
Hamamatsu S10362-11: Terminal Capacitance 35pF
Hamamatsu S10362-33: Terminal Capacitance 320pF
All help is appreciated!
Just from an back of the envelope calculation, a 35pF, photodiode, you will need 4.4GHz gain bandwidth product to achieve >450MHz and a gain of 100ohm. For the 320pF, you will need in excess of 40GHz GBWP.
Could you please send me your requirements by email at firstname.lastname@example.org so that we can see on developing a solution that will satisfy your needs.
In reply to Xavier Ramus:
I found your email exchange by doing a google search on "MPPC time of flight". I am wondering if you have found a good solution using TI opamps. I have a solution using a linear tech opamp (LTC6401-26). While this solution is pretty good, it could be improved. The dynamic range is border line and it would be great if the amplifying circuit input resistance could be < 50 Ohm. I have a pretty accurate SPICE model of the MPPC response if it can be of any help. Anyway, if you are willing to share the solution you developed, I would be very interested.
Thank you. Regards.
Hello! Any development on this subject? I am also working with MPPCs (S10362-11-100U Ct=35 pF, Hamamatsu) and scintillators whose decay time is of the order of 10 ns. I currently intend to optimize the electronics I developed. I use a opa656 as current-to-voltage converter (Rf=10k and Cf=1pF or 10 pF, obtaining a 500ns width pulse ) followed by a ad8000 for gain. How can I improve bandwith?
In reply to Luis Moutinho:
I used THS3201 (current feedback opamp) with 1Kohm or 470 ohm feedback (transimpedance configuration), with short connections stability normaly ok even without extra caps.. If you want to improve bandwith further some improvement possible through use of 10 ohm current sense resistor combined with THS3203 amplification stage. That was done for SensL's SPM (1x1mm and 3x3mm) but should work for Hamamatsu also.
In reply to Nikolai Pavlov:
Sorry i mistyped - THS3203 should be THS4303 device
I doubt than a transimpedance amplifier built with most IC op amps will be sucessful due to the capacitance of your MPPC. Even the GHz- range ONET transimpedance amplifiers probably can't handle even the 35pF of the smallest MPPC.
If you can try a circuit that I've simulated here, maybe it will have the BW that you need but the SNR is a question since I do not know what output pulse peak current you expect to see. Perhaps one could calculate it based on the MPPC efficiency and the electron charge but I'll "leave that to the student as an exercise" as the textbooks always say when the author really doesn't want (or know how) to do it.
Be warned that I have not breadboarded this circuit and that simulations are only as good as the models used.
Regards, Neil P. Albaugh ex-Burr-Brown
In reply to Neil Albaugh:
Peak current for one photoelectron pulse in SIPm/MPPC is typically 5-7uA. It is important to note that SIPM is not a pure capacitor but rather CR circuit. For 1mm it is order of 35pF+300 ohm ..
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