Buffering low capacitance sensors (<50 pF)

I need ideas for buffering a low capacitance sensor (

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Johan van Hespen
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Fred Bloggs

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bill.sloman

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Tim Wescott

The non-inverting input resistance does not necessarily have to match the inverting input resistance. It depends on how much error that you can tolerate due to input bias current. The equation for output error due to input bias current is: . Vob = IbRf(1-Rni/Rinv) Where . Vob is the output error due to bias current . Ib = input bias current . Rf = Equivalent feedback resistance . Rni = Equivalent resistance "seen" by non-inv input . Rinv = Equivalent resistance "seen" by inv input

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Jon

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Ken Smith

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RRogers

Thanks, good idea, did some simulations. Have to be carefull otherwise the circuitry turns into a oscillator.

Reply to
Johan van Hespen

I do not have stringent DC offset requirements. The sensor used is small area PVDF pressure sensor (capacitance usually less then

Reply to
Johan van Hespen

I meant CLC425. I think the OPA656 has not so good noise figures

Reply to
Johan van Hespen

This is what I do know, I tolerate a certain output error but due to this there is a limitation in this Rf

Reply to
Johan van Hespen

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