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The output current of a transistor depends upon the input current. Hence, the transistor is called as current controlled device.

The zero signal collector current and collector to emitter voltage is called quiescent point.

Leakage current is the current through a device due to the motion of minority charge carriers under reverse based condition.

Transistor biasing is the application of suitable DC voltages across the transistor terminals.

A transistor with its terminals not connected to any source is called an unbiased transistor.

(i) Q point gets stabilised very well as the stabilication factor does not
depend upon p.

(ii) It provides better amplification when used in amplifiers.

Leakage current is current through a device due to the motion of minority charge carriers under reverse bias conditions.

Different leakage currents are:

(i) Collector to base leakage current with emitter open (I_CBO).

(ii) Collector to emitter leakage current with base open (1_CEO).

Operating point is the zero signal values of collector I_c and collector to emitter voltage V_CE of a transistor. DC load line is a straight line drawn on the output characteristics representing output DC voltage and corresponding direct current under no signal conditions.

Load line is a straight line drawn on output characteristics representing output DC voltage and corresponding output direct current under no signal condition. Load line contains every possible operating point for the circuit.

Heat sink is a device which absorbs unwanted heat generated in the transistor and radiates to the surroundings. A copper conductor with different shapes are connected to the device to take out heat from the device. With heat sink, power rating of the device increases.

The value of p and temperature.

The self destruction of an unbiased transistor due to increase in temperature and hence increase in leakage current.

Voltage divider biasing circuit.

The operating point does not depend upon the value of β of the transistor. Hence the operating point does not change its position due to rise in temperature or replacing a transistor of different p value. Hence voltage divider bias provides excellent stabilisation and is preferred to other biasing methods.

Unbiased transistor is a transistor with its terminals not connected to any source. Biasing a transistor is applying a suitable DC voltage across the transistor terminals to operate the transistor in the desired region.

Need for biasing a transistor are:

(i) To make operating point to be at the centre of load line for faithful amplification.

(ii) To make collector current independent of temperature variations.

(iii) To make operating point stabilised even when one transistor is replaced by another.

(i) Fixed bias

(ii) Collector to base feedback.

The application of suitable DC voltage across the transistor terminals is called biasing of the transistor.

The reasons for biasing of a transistor are:

(i) To make the operating point to be at the centre of the load line.

(ii) To make the collector current independent of temperature variations.

(iii) To maintain the operating point constant even though transistor is replaced by another of same type.

Fixed bias is biasing circuit.

Different biasing circuits are:

(i) Fixed bias

(ii) collector to base bias.

(iii) Emitter feedback bias.

(iv) Voltage divider bias.
voltage divider biasing circuit is the best method to get faithful amplification.