Electronics > Projects, Designs, and Technical Stuff
High Speed Transimpedance Amplifier
StillTrying:
http://www.ti.com/lit/ug/tidud08/tidud08.pdf
They've got about 900uA in the fast PD, which is about 200 million times higher than the OP's 5pA.
Alex Nikitin:
OK, a bit of a reality check.
An MCP can have (conservatively) a gain of ~1000. For each electron entering it will produce ~1000 electrons output . That is the minimum charge you need to detect. If the output pulse width is ~2ns it creates a current of ~ 30uA for that duration, detectable even on a good fast scope with a 50 Ohm input as a ~1.5mV pulse. ~80nA, 1pA to 5pA output current will be averaged from these fast current pulses. 100 pulses / second will create an average current of ~6pA . The only way to measure this current reliably is to either integrate it over a long time (i.e. seconds) or count the pulses. What the TS needs is not the current measurement as such, I suspect, but the timing of pulses. That is not a difficult task and you only need a low gain transimpedance amp (or even just a resistor load and a fast voltage amplifier), so the bandwidth is not a problem either.
Cheers
Alex
P.S. - corrected the calculations, had a senior moment apparently :palm:
Marco:
That's fine, but that's not his spec. It does make sense though, why use an electron multiplier and then spec an amplifier for single electrons within your bandwidth.
arivalagan13:
Thank you all for the response...I would like to add a few more information so that I can get more information from you.
I've installed 1Gohm resistor...but while testing with the instrument in the lab I will sweep the resistors (desolder and solder) with values ranging from 10ohm, 1kilo ohm, 2.5kilo ohm and many more...I'll do this exercise to understand the system requirements more precisely...it is one of the govt. labs which use the analytical instrument(time-of-flight mass spectrometer)... I am attaching the graph for your reference...
Also, the lab at present uses the amplifier 6950ds(attached) from Phillips Scientific. I need a better performance than this...
I'll go iteratively...
One of my questions is like suppose I want to test the amplifier in the lab with a function generator (which generates a voltage signal) how do I generate a current signal for testing purposes..I never used or have access to advanced measuring instruments and so I am asking about it
Kindly give me further suggestions and input..also, suggest some information regarding noise and input capacitance of the opamp
arivalagan13:
Adding one more graph for your reference
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