Page 43 - Semester-IV-Electronics

 Usually, the circuit of an oscillator has an amplifier in which in its

input or output circuits or in both oscillatory tank circuits are

provided.

 Any electrical jerk, as switching on the electrical supply, starts

electrical oscillations of negligible amplitude in the tank circuit.

 The amplifier amplifies these oscillations and if a part of output

voltage is fed back as positive feedback, the amplitude of oscillations

goes on increasing.

 At a certain stage, the rate of energy fed back in the oscillatory

circuit becomes equal to the arte at which energy is dissipated. In this

state, the amplitude of oscillations becomes constant. Such an

oscillator is called feedback oscillator.

 Thus, a feed back oscillator is a positive feedback amplifier whose

resultant voltage gain is infinite.

 If in the oscillatory circuit, a device is used annulling the source of

energy loss or resistance due to which voltage increase with decrease

in current. 43