The Clapp circuit

A variation of Colpitts oscillator uses series resonance, rather than parallel resonance, in tuned circuit. Else, circuit is basically the same as the parallel-tuned Colpitts oscillator. A diagram of an N-channel JFET Clapp oscillator circuit is shown in the figure given below. The P-channel circuit is identical, except the power supply polarity, which is reversed.The bipolar-transistor Clapp circuit is exactly the same as the circuit of given in the figure, with the emitter in place of the source, the base in place of gate, and the collector

                         Figure-- Colpitts oscillators. At point A, NPN bipolar transistor; at point B, N-channel JFET.

in place of drain. The only difference, is the addition of a resistor between the base and the positive supply voltage or the negative supply voltage. The Clapp oscillator provides excellent stability at RF. Its frequency will not change much when high-quality components are taken in use. The Clapp oscillator is a reliable circuit;