The Colpitts Oscillator
The Colpitts Oscillator, named after its
inventor Edwin Colpitts is another type of LC oscillator design. In many ways,
the Colpitts oscillator is the exact opposite of the Hartley Oscillator we
looked at in the previous tutorial. Just like the Hartley oscillator, the tuned
tank circuit consists of an LC resonance sub-circuit connected between the
collector and the base of a single stage transistor amplifier producing a
sinusoidal output waveform.
basic configuration of
the Colpitts Oscillator resembles that
of the Hartley Oscillator but the
difference this time is that the centre tapping of the tank sub-circuit is now
made at the junction of a "capacitive voltage divider" network
instead of a tapped autotransformer type inductor as in the Hartley oscillator.