I am attempting to build the following circuit using an LM6171 op-amp. I know that this op-amp is unity-gain stable. I previously had this circuit working with an LT1637 op-amp, but I had to switch parts for a higher GBWP.
simulate this circuit – Schematic created using CircuitLab
I want to put a low amplitude sine wave (10 mV, peak-peak) on the input. The output is connected to a low impedance load (< 10 ohms) through a relay, which is normally off (so normally open circuit).
When I switch on the power, the output shows a ~20 V, 20 MHz sine wave (without me applying any voltage to the input). Why is this op-amp oscillating? I am not sure what part of the datasheet would give me a clue here – I figured that the main issue was the phase margin.
Best Answer
Try something more like this- you may have to fiddle with the value of the capacitor to optimize it if you need really high frequency response.
simulate this circuit – Schematic created using CircuitLab