oscillator It is an electronic device that produces electrical oscillations. The output of an oscillator is fed back into the input through a feedback circuit, in correct phase. In fig.o1, a schematic diagram of an amplifier in which feedback supplies the entire input is shown.

From the figure,

V_f = V_i = b V_o = - Ab V_i

Þ (1+Ab ) V_i = 0

Þ (1+Ab ) = 0

Þ Ab = - 1+ i.0 (Berkhausen criterion) (o3)

Therefore the basic requirement of the oscillator are,

(a) the feedback factor ú Ab ú =1;

(b) net phase shift around the loop must be integral multiple of 2p .

Two standard forms of oscillator circuits are shown in fig.o2 and fig.o3.