One last experiment I wanted to do after the recent sine wave circuits, was to compare a few different op-amps.
I’m including the original one here as well – the LM358, running at ±13.6V:
Here’s the LT1413, running at ±14.4V:
And here’s the NE5532ANG, running at ±15.3V:
In each case, the supply voltage was adjusted until the output sine wave was ±10 V, with all other components identical. Note the slight difference in oscillation frequency.
What’s also interesting, is the mean output voltage: it should be 0V with an ideal circuit. Looks like the NE5532ANG performs best – within 1%. It’s described as being an “Internally Compensated Dual Low Noise Operational Amplifier”. Second harmonic is at -51 dB
m, i.e. 0.28% harmonic distortion – an excellent signal!
As a quick test with that last op-amp, I reduced the supply voltage to ±2.5V – the effect was a slightly higher frequency of 522 Hz, a much lower output of 2.14 Vpp, i.e. ±1.07V, but relatively far off-center: 240 mV. Harmonic distortion rises to 3.5% in this case. But that’s not surprising: the NE5532ANG is only specified down to ±3V, and it’s not a “rail-to-rail” op-amp, which means it cannot generate an output voltage too close to its supply voltage (with a ±5V supply, distortion drops back to 1.25%).
Lots of op-amps. Lots of trade-offs.
Ok enough op-amp chit-chat for now, I’ll stop :)