Question

Describe briefly the underlying principle of a transistor amplifier working as an oscillator. Hence, use the necessary circuit diagram to explain how self sustained oscillations are achieved in the oscillator.

Answer 1

Hint:Here we need to follow the principle of self -sustained oscillation, means vibration in which forces outside the system are controlled by the system to maintain the system's periodic vibration at a period or frequency that is almost the natural period of the system.

Complete answer:
In a transistor an oscillator must have all three elements: oscillatory element or circuit, amplifier, and feedback network. The oscillating circuit or element consists of an inductor coil of inductance L that is connected in parallel with a capacitor of capacitance C. The frequency of oscillation in the circuit depends on the values ​​of L and C.
The actual frequency of oscillation is the resonant or natural frequency and is given by
${\text{f}} = \dfrac{1}{{2\pi \sqrt {LC} }}$
​where L is inductance of coil in henrys, and C is the capacitance of capacitor in farads.
The electronic amplifier gets dc power from the battery or dc power flexibly and changes over it into ac power for supply to the tank circuit. The motions happening in the circuit are applied to the input of the electronic amplifier. Due to the amplifying properties of the speaker, we get expanded yield of these oscillations. This amplified yield of oscillations is a direct result of dc power provided from the outer source (a battery or force flexibly). The output of the amplifier can be provided to the tank circuit to meet the losses.
The feedback network supplies a part of output power to the tank or oscillatory circuit in the correct phase to aid the oscillations. In other words the feedback circuit provides positive feedback.

Information: Sustained oscillation is a special type of vibration in which each cycle of vibration is similar to the previous cycle. In control theory, continuous vibration means that the vibration continues due to insufficient damping of the reaction path, the force acting is outside the system, but controlled by the system, maintains the periodic oscillation of the system at a period or frequency that is the natural period of the system. Here is an example of sustained oscillation, showing the behavior of a stock exhibiting sustained oscillation over the course of 12 time units.

Note:Transistors are semiconductor devices used to amplify or switch electronic signals and power. It is usually made of a semiconductor material with at least three terminals for connecting to external circuits.
Amplifiers are used to increase the amplitude of a signal waveform without changing other parameters of the waveform, such as frequency or waveform. These are one of the most commonly used circuits in electronic devices and perform different functions in a large number of electronic systems.