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Introduction

Table.: Difference between voltage amplifier and power amplifier

Voltage Amplifier

Power Amplifier

A small-signal amplifier can use only 10% of ac load line for operation. These amplifiers are known as voltage amplifiers.

A large-signal amplifier uses a large part of ac load line for proper operation.

The current gain β of a transistor used in voltage amplifier is very large. The typical value of β is about 100.

The current gain β of a transistor used in a power amplifier is less than a voltage amplifier. The typical value of β  is in the range of 20 to 50.

The input resistance of a voltage amplifier is low compared to output resistance.

The input resistance of a power amplifier is very large compared to output resistance.

The size of transistor used in a voltage amplifier is small. These transistors are known as low- or medium-power transistors.

The size of a transistor used in a power amplifier is large. A certain amount of heat is dissipated within the transistor, provided with a large cooling surface area required for heat dissipation. These transistors are known as power transistors.

In a voltage amplifier, RC  coupling is used for inter-stage connection.

Transformer coupling is used for a power amplifier.

For analysis of small-signal amplifiers, the h-parameter (linear) model of a transistor is used.

For analysis of large-signal amplifiers, the output characteristic graphs of a transistor is used. The nonlinearity existing due to the output characteristics are not equidistant.





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