Hi all,
I would like to add an over-voltage protection resistor (Rp) for my AD549 op amp, which is occasionally subjected to 35 V at its inverting input. The op-amp is supplied +/- 5 V.
The manual indicates that Rp should be chosen to limit the current to 100 uA.
I am not quite sure how to choose the right resistor, because the op-amp itself has a significant input resistance.
Today, I tried a 1 MOhm resistor (wanted ~300 kOhm instead), but this seemed to add a few standard deviations of noise, in addition to what seemed like a drifting voltage (or slow response) at the op-amp output.
Figures:
Op Amp over-voltage.png -my circuit without Rp
AD549.png -from manual
Any sugestions?
Adam
I would like to add an over-voltage protection resistor (Rp) for my AD549 op amp, which is occasionally subjected to 35 V at its inverting input. The op-amp is supplied +/- 5 V.
The manual indicates that Rp should be chosen to limit the current to 100 uA.
I am not quite sure how to choose the right resistor, because the op-amp itself has a significant input resistance.
Today, I tried a 1 MOhm resistor (wanted ~300 kOhm instead), but this seemed to add a few standard deviations of noise, in addition to what seemed like a drifting voltage (or slow response) at the op-amp output.
Figures:
Op Amp over-voltage.png -my circuit without Rp
AD549.png -from manual
Any sugestions?
Adam