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

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Discussion Overview

The discussion revolves around techniques for amplifying a low input voltage (1nA) at high frequencies (10,000kHz to 1MHz) using operational amplifiers (op-amps). Participants explore methods to reduce noise in the amplification process, considering the limitations of their current setup and the characteristics of op-amps.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about tricks or techniques to reduce noise from op-amps while amplifying a low current signal at high frequencies.
  • Another participant points out that the original question had been posted previously and suggests that it should be in the Electrical Engineering forum.
  • A participant expresses frustration that the provided answers in the previous thread were not feasible for their situation.
  • There is a contention regarding the understanding of bandpass filters, with some participants arguing about the definition and application of such filters in the context of the discussion.
  • One participant notes that op-amps may function as low-pass filters at higher frequencies, where gain decreases, and mentions that attempts to use high-pass filters did not significantly reduce noise.
  • The participant questions whether their noise issues are limited by the type of op-amp being used.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness and understanding of bandpass filters, as well as the limitations of their current op-amp setup. There is no consensus on the best approach to reduce noise in the amplification process.

Contextual Notes

Participants have not reached a resolution regarding the most effective methods for noise reduction, and there are unresolved questions about the suitability of their op-amp choice and filter applications.

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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