In this theory-based episode, we look at what it takes to make a Colpitts oscillator produce a sine wave. We cover Barkhausen’s criteria in order to keep the oscillation going, a basic NPN transistor amplifier which controls the gain, and calculating the resonance of the LC circuit’s feedback network. Though there are better options for a more spectrally pure and accurate sine wave, the common-emitter BJT Colpitts makes for a good building block and starting point when learning about oscillators.
