Oscillator Delivers Four Multi-Phased, Equal-Amplitude Sine Waves

摘要

I thought the solution would look like a common three-op-amp phase-shift oscillator, so that was my starting point. Three RC stages, all equal and running at a 60° phase delay, would sum to the 180° phase shift required for oscillation. For symmetry's sake, I used the fourth op amp in a quad device to buffer the final RC stage prior to feeding back to the summing amplifier. This way the feedback impedance doesn't load the RC oscillator and affect the phase shift of the last stage.