(a) Explain briefly the principle on which a transistor-amplifier works as an oscillator, Draw the necessary circuit diagram and explain its working.
(b) Identify the equivalent gate for the following circuit and write its truth table.
a) Principle : A portion of the output power is returned back (feedback) to the input in phase with the starting power (This process is termed as positive feedback) (1/2) marks
As the switch is put on, a surge of collector current flows in the transistor. This current flows through the coil . The inductive coupling between coil and coil now causes a current to flow in the emitter circuit . As a result of this positive feedback, the emitter current also increases . When the current in becomes saturated , it stops increasing. Now emitter current begins to fall and becomes minimum. The whole process keeps on repeating itself. (1) marks
b) AND Gate