**Tuned Drain Oscillator – Circuit Diagram and Equation:**

Tuned drain oscillator is similar to the tuned collector oscillator, and the basic circuit is given in Fig 21.10.

Because of its high input impedance and high voltage gain, an FET can be used to build up very simple and efficient oscillator circuit. The frequency of oscillation is given by

where r_{d} is ac drain resistance.

The value of mutual inductance required for maintaining oscillations is given by