1). What is a Power Amplifier?
A power amplifier amplifies weak signal until it has enough power to drive an output device, such as a loudspeaker.
2). What are the Characteristics of a Power Amplifier?
- Impedance matching to provide maximum power to load.
- Power transistors are required to tolerate high voltage and current.
- Power amplifiers are bulky.
- Harmonic distortions are caused by transistors’ nonlinearity.
3). Define the Circuit Efficiency
Circuit Efficiency is defined as ratio of alternating current output power to direct current input power. It is also known as the Figure of Merit.
η = (AC Power/DC Power) x 100%
4). What is meant by class of amplifier?
When driven by a sinusoidal input signal, amplifier classes describe the degree of variation in the output signal throughout one cycle of operation.
5). What is a Class A power amplifier?
A power amplifier is called a class A amplifier if transistor in the circuit conducts for the entire cycle of the input signal. The operational point is chosen about in the center so that output current follow input signal.
6). Describe the advantages and disadvantages of a class A power amplifier
Advantages
- Simple structure.
- Distortion-free output voltage
Disadvantages
- Extremely low efficiency (25%).
- High power dissipation in transistors.
- Higher output impedance
7). What is a Power MOSFET?
Power MOSFET is a type of MOSFET that is specifically engineered to deal with high power levels.
Power MOSFETs are frequently employed in power devices because of the following features.
- Reduced gate drive power.
- High switching speed
- Parallel operation.
8). What are the different types of Distortion
- Amplitude distortion.
- Frequency Distortion
- Delay (or)Â phase shift distortion.
- Crossover distortion.
9). Define Velocity Saturation
The high electric field in the short channel causes the velocity of the charge carriers to be maximized. This is referred to as velocity saturation.
10). What is a DC-DC Converter?
DC-to-DC converters convert one level of the DC voltage to another. It is also referred as a DC Chopper.
11). What are the different applications for DC Choppers?
- Traction motor control for electric vehicles, trolley cars, marine hoists, trucks, and mine haulers. They supply smooth acceleration control, excellent efficiency, and rapid response.
- Regenerative breaking of the motors to restore energy to the supply, resulting in energy savings for transportation with regular stops.
- DC voltage regulators.
12). How do you define a Buck Converter?
Buck Converters, which is known as step down converters, provide a lower output voltage than the input voltage.
The average output voltage is lower than the input voltage.
13). Describe the uses of the Buck Converter
- Utilized to drive high current loads; utilized in PCs and motherboards.
- Battery Chargers
- Solar Chargers
14). Define Boost Converter
The boost regulator generates an output voltage higher than the input voltage.
15). What is a Buck-Boost Converter?
A buck-boost regulator generates an output voltage that can be less than or larger than the input voltage.
The polarity of the output voltage is the opposite of the input voltage. This regulator is commonly referred as the inverting (or) flyback regulator.
16). Write on the advantages of Converter
- Needs only one transistor.
- Simple construction.
- High efficiency.
- Less expensive
17). Why do we need a Power Amplifier?
When a high quantity of power must be provided to a load, power amplifiers are utilized.
18). Define Cross-Over Distortion
Near the zero crossing points, neither transistor Q1 nor Q2 conducts, resulting in a gap between the positive and negative halves of the output signals. As a consequence, the output waveform is discontinuous. This distortion is known as cross-over distortion.
19). What is the Circuit Turn-Off Time?
The term “circuit turn-off time” refers to the period of time during which a voltage in the reverse direction is applied over the thyristor during the operation of commutation.
20). Why should circuit turn-off time be longer than thyristor turn-off time?
To ensure dependable turn-off, the circuit turn-off time must be greater than the thyristor turn-off time. Otherwise, the device may turn on unexpectedly, known as commutation failure.
21). What is meant by Phase Controlled Rectifier?
It takes a constant alternating current (AC) voltage and transforms it into a variable direct current (DC) voltage.
22). What is meant by Delay Angle?
The delay angle is defined as the angle formed by the zero crossing of input voltage & the instant the thyristor is activated.
23). What is Commutation Angle (or) Overlap Angle?
The commutation interval during which outgoing and arriving thyristors transact is known as the overlap period. The commutation angle, or overlap angle, refers to the angular time during which two devices share conduction.
24). What is Displacement Factor?
For linear loads that have sinusoidal voltages and currents, the displacement factor equals the power factor.
25). What is meant by Step-Up and Step-Down Chopper?
A step-down chopper (or) Buck converter has an average output voltage that is lower than the input voltage.
In a step-up chopper (or) Boost converter, the average output voltage exceeds the input voltage.
