Op-amp circuits and noise at high frequency/low amplitude

AI Thread Summary
The discussion focuses on amplifying a 1nA input voltage at frequencies between 10kHz and 1MHz while minimizing noise from op-amps. Techniques such as using multiple op-amp stages and filters have been explored, but noise reduction has not been significant. The user expresses frustration with previous advice, particularly regarding bandpass filtering, and questions whether the op-amp's limitations contribute to the noise issue. Suggestions for reducing noise beyond filtering are sought, indicating a need for alternative strategies. Overall, the challenge lies in effectively amplifying a low-amplitude signal while managing high-frequency noise.
GuitarOfWar
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Hi everyone.

I am tasked with amplifying an input voltage of around 1nA at anywhere between 10,000kHz to 1MHz to a sufficient amount. We've been using op-amps in multiple stages in series to amplify the signal. At our disposal we have a function generator, oscilloscope, breadboard and resistors, capacitors etc. Are there any tricks or techniques I can use to reduce the noise from the op-amps?
 
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GuitarOfWar said:
I can't bandpass the signal because the input is meant to be simulating particles hitting a plate at a frequency of say 10000kHz to 1MHz.

You're wrong. it sounds like you have a false idea of what bandpass filter means. The word "band" means a range of frequencies, such as 10kHz-1MHz.
 
anorlunda said:
You're wrong. it sounds like you have a false idea of what bandpass filter means. The word "band" means a range of frequencies, such as 10kHz-1MHz.
Doesn't the op amp kind of work as a low pass filter? At frequencies about 1.5-2MHz+ the gain starts decreasing any way. Also we tried using high-pass filter with an RC circuit that only allows frequencies above 10,000kHz to pass and the amount of noise reduced wasn't dramatic. Is there any other tricks I can use to eliminate noise which aren't just using a filter or is my task limited by the type of op-amp I am using?
 
I posted an answer in the original thread.
 

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