I've been testing this circuit configuration with the THS4021 op-amp, which is "stable at a gain of 10 (-9) or greater" according to its datasheet, and I can see that it's true for certain low gains. There is a lot of voltage oscillation at the output when R1 is set to a value below 200 ohms, but for R1 = 250 ohms or 300 ohms for example, the circuit seems to work fine and I get no oscillation in my output. Why is that? And does that mean I can use this exact set-up in my design or should I select a different op-amp if I am looking for a gain of -4 V/V? I've attached the waveform for reference.