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Identifying the best Diff-Amp for one's design?

Shing Luk
Prodigy 10 points

I need a fully diff amp that can take in a 20Vpp single-ended bipolar signal, output that signal in differential form, without gaining or attenuating, and meet an input impedance requirement of >1Meg and have a bandwidth of >200kHz? Thanks in advance.

  • 0
    Intellectual 410 points
    While you could use very high value feedback resistors, it eats your input noise budget (1 Mohm is 129 nV/rtHz), and generally when people write ">1M input impedance" they want a non-inverting op-amp input. Which means that you'll need at least two op-amps, one to buffer the signal and the second to do the single-ended-to-differential diff-amp bit. While you could use a fully differential op amp for the second bit, I generally prefer to use a simple unity gain diff-amp, with its reference input driven by a G=-1 i inverting amplifier on its main output. If following stages have any sort of CMR, the performance of the latter is not critical, as the diff amp makes sure that (out+ - out-) has the right value.
  • 0
    Genius 5430 points

    Shing;

    I would use a fully differential amplifier in unity gain with an op amp voltage follower on each input. The input impedance will be extremely high and you will have differential input & output. Your differential gain will be 1V/V.

    Regards, Neil   ex-Burr-brown