types of amplifiers

What are the Types of amplifiers?

There are four types of amplifiers based on input signal fed to it and the output signal extracted from it. They are

  • Voltage amplifier
  • Current amplifier
  • Trans conductance amplifier
  • Trans resistance amplifier

Define Transconductance, Transresistance, voltage gain, current gain?

Voltage gain of an amplifier is defined as ratio of output voltage to input voltage fed to amplifier. It is unit less and is denoted by Av.

                                                 Voltage gain Av = Vo/Vi

Current gain of an amplifier is defined as ratio of output current to input current fed to amplifier. It is unit less and is denoted by Av.

                                                 Voltage gain Ai = Io/Ii

Transconductance of an amplifier is defined as ratio of output current to input voltage fed to amplifier. It is specified in units of mhos (or) Siemens and is denoted by Rt.

                                       Transconductance Rt = Vo/ Ii

Trans-resistance of an amplifier is defined as ratio of output voltage to input current fed to amplifier. It is specified in units of ohms and is denoted by Rt.

                                       Trans-resistance Rt = Vo/ Ii

What are the Ideal input and output resistances of various amplifiers?

Parameter/Type of amplifier Voltage amplifier Current amplifier  

Transconductance

amplifier

Transresistance

amplifier

Input resistance Infinite Zero   Infinite Zero
Output resistance Zero Infinite   Infinite Zero

What is an Audio amplifier?

Audio amplifiers are electronic power amplifiers used to amplify low intensity audio signals to a level suitable to drive loud speakers. The audio frequencies are in the range 20 Hz to 20,000 Hz. Normally Class AB power amplifiers are used to do audio amplification. Phase distortion will not create much problem in audio amplifiers.

What is a Video amplifier?

These amplifiers are use to amplify video signals. These amplifiers have varying bandwidths based on the type of filter used at each point. Typically a low-pass amplifier will be having a bandwidth in the range from 2 to 10 MHz. Some of the applications are in television receivers, cathode-ray-tube computer terminals, and pulse amplifiers. The phase distortion is of prime concern in video amplifiers; hence extra elements are added to nullify distortion.

What is Power amplifier?

A power amplifier stage is an amplifier optimized to deliver high output power. Special attention has to be paid in designing such amplifiers as the power dissipation across the junction raises its temperature and eventually destroys it. In practice we can observe that the power transistors are bulky in nature to handle high powers as high surface area leads to high heat removing capacity.

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