Driving AD9240

Our application is driving the AD9240 14 bit 10MHz A/D.This is an instrumentation application so settling time, low noise and low drift are the more critical parameter. The goal is to have switchable gains up to 1000x using multiple stages. The input could be a square wave or pulse mixed with random noise.

Using the parametric search the ADA4895-1 and/or AD8021 appear to be the top choices with limits of 3nV/rtHz, GBP > 130M, The AD8099 and AD829 met those but the VosTC was 10x or more higher than the others.

Suggestions and comments welcome.

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Note: The AD9240 was selected for compatibility with the test platform. Ultimately one of the newer serial A/Ds will be used, 20MHz or faster so an amplifier chain that can support the higher speeds is of interest.

Scott

Parents
  • I would like to be able to limit the bandwidth of the ADA4895-1 op-amp. Is there a limit to how large the feedback capacitor can be used on an op-amp that is not unity gain stable? For example using the ADA4895-1, minimum stable gain of 10x, could a feedback capacitor cause the op-amp to oscillate?

    226 ohm feedback resistor

    25.5 ohm gain resistor

    35pF feedback capacitor

    Scott

Reply
  • I would like to be able to limit the bandwidth of the ADA4895-1 op-amp. Is there a limit to how large the feedback capacitor can be used on an op-amp that is not unity gain stable? For example using the ADA4895-1, minimum stable gain of 10x, could a feedback capacitor cause the op-amp to oscillate?

    226 ohm feedback resistor

    25.5 ohm gain resistor

    35pF feedback capacitor

    Scott

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