The OPA2134 datasheet indicates that, in non-inverting configuration,
the impedance seen by both inputs should be matched to minimize
distortion if either of them is > 2 kohm. So, if I have a unity gain
Sallen Key filter where the source impedance (in the passband) is
around 27 kohm, should I put a 27k resistor (rather than a short)
between output and inveting input? I guess in theory I should but I
don't think I've ever seen this done, and if I'm not mistaken this
problem of increased distortion with different Zs at the inputs is
common to many FET opamps, not just the 2134.
Many thanks in advance,
Carlos
the impedance seen by both inputs should be matched to minimize
distortion if either of them is > 2 kohm. So, if I have a unity gain
Sallen Key filter where the source impedance (in the passband) is
around 27 kohm, should I put a 27k resistor (rather than a short)
between output and inveting input? I guess in theory I should but I
don't think I've ever seen this done, and if I'm not mistaken this
problem of increased distortion with different Zs at the inputs is
common to many FET opamps, not just the 2134.
Many thanks in advance,
Carlos