I have a circuit where I'm amplifying the output of a piezo transducer with an op-amp. By taking some readings, i've found that the piezo can output fairly high voltages when struck hard (~20V), and so I want to protect the op-amp against high currents.
To that end I thought about including a resister in series with the op-amp's non-inverting input, but I'm unsure on a few things. Namely, my questions are:
- What value to use for resistor (R1 below), and how to calculate it?
- How much current will be flowing through the op-amp due to the high voltage spike?
- What's the maximum current the op-amp can handle on the non-inverting input?
Below I've drawn up a simple schematic to represent my circuit - I've used a 1Ω resitor to represent the load, but in actuality the output signal will be fed into an op-amp comparator and then into a microcontroller subsequently:
Thanks for your help!