Bias Circuit, Driver Circuit
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
Class AB amplifier can be designed using MOSFET to generate an output power of 100 W. This amplifier has high efficiency and less harmonics. This circuit consists of drivers, bias circuit and power amplification using MOSFET with class AB amplifier MOSFET is preferred over BJT because of its simple drive circuit, less susceptibility to thermal stability and high input impedance.
Comparison of Power MOSFET and Power BJT
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
This indicates that thermal runaway will not occur in MOSFET even if operated beyond zero temperature coefficient. In low current region (< zero temperature coefficient), the temperature coefficient of iD is positive and thermal runaway occurs.
Construction, Operation, Characteristics
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
Power MOSFET is a special type of MOSFET designed to handle high power levels. Power MOSFET are commonly used power devices due to the following advantages. 1. Low gate drive power 2. Fast switching speed 3. Parallel operation
Comparison of Power Amplifiers
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
If the output of an amplifier is not a complete sine wave, then it is known as distortion using Fourier analysis, any distorted periodic waveform can be broken into different frequency components. These components are known as harmonics of the fundamental frequency. Harmonics are integer multiples of a fundamental frequency. For example. 1st harmonic is 1 x F KHz.
Construction, Advantages, Disadvantages, Applications
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
Class C amplifier are biased deep into cut off. The negative voltage at the base terminal reverse-biases the base-emitter junction of the transistor such that it will not conduct until the input signal overcomes this reverse bias.
Construction, Operation, Advantages, Disadvantages
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
To overcome the cross over distortion in class B amplifiers, we are going for class AB amplifiers. The output signal is obtained for more than 180° but less than 360° of the ac input signal.
Class B Complementary Symmetry Amplifiers, Comparison of Push-Pull and Complementary Symmetry Amplifiers
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
The circuit uses two transistors one is NPN and other is PNP. It is a transformer less circuit. Symmetry indicates that biasing resistors are equal.
Class B Push Pull Amplifier
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
The main drawback of class A amplifier is that all of the supply power is dissipated in the transistor when there is no input.
Construction, Advantages, Disadvantages
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
Instead of connecting the load directly, the output is connected to the load through a transformer. This is used for impedance matching and is used for low impedance s like loudspeakers.
Derivations, Advantages, Disadvantages
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
A power amplifier is known as class A amplifier if the transistor used in the circuit conducts for full cycle of the input signal. The operating point is selected approximately at the center so that the output current follows the input signal.
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
Amplifier classes represent the amount of output signal variation over one cycle of operation when excited by a sinusoidal input signal.
Comparison of Small Signal and Large Signal Amplifiers
Subject and UNIT: Electronic Devices and Circuits: Unit V: Power Amplifiers and DC/DC Converters
The voltage amplifiers operate in the linear portion of the transfer characteristics, closer to Q-point of the amplifier. These amplifiers are called small signal amplifiers because they are mainly used for voltage amplification but not used for providing large power to the loads.