Nautical Electronics - Amplifiers

Flashcards for review of lecture notes on amplifiers.

Amplifier

An electronic circuit used to increase the strength of a weak input signal in terms of voltage, current, or power.

Amplification

The process of increasing the strength of a weak signal.

Single-stage Amplifiers

Amplifiers with only one transistor circuit, providing single-stage amplification.

Multi-stage Amplifiers

Amplifiers with multiple transistor circuits, providing multi-stage amplification.

Voltage Amplifiers

Amplifier circuit that increases the voltage level of the input signal.

Power Amplifiers

Amplifier circuit that increases the power level of the input signal.

Small signal Amplifiers

Amplifier where the input signal is so weak that it produces small fluctuations in the collector current compared to its quiescent value.

Large signal amplifiers

Amplifier where the fluctuations in collector current are large, beyond the linear portion of the characteristics.

Audio Amplifiers

Amplifier circuit that amplifies signals in the audio frequency range (20Hz to 20 KHz).

Radio Power Amplifiers

Amplifier circuit that amplifies signals in a very high frequency range.

Class A amplifier

Biasing conditions are such that the collector current flows for the entire AC signal applied.

Class B amplifier

Biasing conditions are such that the collector current flows for half-cycle of input AC signal applied.

Class C amplifier

Biasing conditions are such that the collector current flows for less than half cycle of input AC signal applied.

Class AB amplifier

Combining both class A and class B in order to have all the advantages of both the classes and to minimize the problems they have.

RC Coupled amplifier

Multi-stage amplifier circuit coupled to the next stage using resistor and capacitor (RC) combination.

Transformer Coupled amplifier

Multi-stage amplifier circuit coupled to the next stage with the help of a transformer.

Direct Coupled amplifier

Multi-stage amplifier circuit coupled to the next stage directly.

Common Emitter Amplifier

A three basic single-stage bipolar junction transistor and is used as a voltage amplifier.

Biasing Circuit

Resistors that form the biasing and stabilization circuit, which helps in establishing a proper operating point.

Input Capacitor (Cin)

Capacitor that couples the input signal to the base of the transistor, allowing AC signal but isolating from R2.

Coupling Capacitor (CC)

Capacitor present at the end of one stage, connecting it to the other stage, blocking DC but allowing AC to pass.

Emitter by-pass capacitor (CE)

Capacitor employed in parallel to the emitter resistor, bypassing the amplified AC signal.

Load resistor (RL)

The resistance connected at the output.

DC equivalent circuit of CE amplifier

DC equivalent circuit of CE amplifier created by removing all the capacitors in CE amplifier circuit.

Small Signal Model

Small signal model accounts for the behavior which is linear around an operating point. When the signal is large the behavior becomes non linear.

Frequency response

The curve drawn between voltage gain and signal frequency of an amplifier.

Roll-off section of the frequency response curve

The output at the two cut-off frequency points will decrease from 0dB to -3dB & continues to drop at a fixed rate.

Cascading

The connection of two amplifier stages using a coupling device is called…

Resistance-Capacitance Coupling

This is the mostly used coupling method, formed using simple resistor-capacitor combination.

Impedance Coupling

The coupling network that uses inductance and capacitance as coupling elements.

Transformer Coupling

The coupling method that uses a transformer as the coupling device.

Direct Coupling

If the previous amplifier stage is connected to the next amplifier stage directly.

Feedback

A fraction of output energy of some device is injected back to the input.

Positive Feedback

Feedback in which the feedback energy is in phase with the input signal and aids it.

Negative Feedback

Feedback in which the feedback energy is out of phase with the input and opposes it.

Voltage-Series Feedback Amplifier

A fraction of the output voltage is applied in series with the input voltage through the feedback circuit.

Voltage-Shunt Feedback Amplifier

A fraction of the output voltage is applied in parallel with the input voltage through the feedback network.

Current-Series Feedback Amplifier

A fraction of the output voltage is applied in series with the input voltage through the feedback circuit

Current-Shunt Feedback Amplifier

A fraction of the output voltage is applied in series with the input voltage through the feedback circuit.

Voltage Amplifier

The level of signal is raised.

Power Amplifier

The level of power is raised and is required to deliver a large amount of power and has to handle large current.

Audio Power Amplifiers

Raises the power level of signals that have audio frequency range (20 Hz to 20 KHz).

Class A Power amplifier

The collector current flows at all times during the full cycle of signal.

Class B Power amplifier

The collector current flows only during the positive half cycle of the input signal.

Class C Power amplifier

The collector current flows for less than half cycle of the input signal.

Mode of operation

The portion of the input cycle during which collector current flows.

Collector Efficiency

It explains how well an amplifier converts DC power to AC power.

Distortion

Change in output wave shape from the input wave shape of the amplifier

Class A power amplifier

The output current flows for the entire cycle of the AC input supply.

Transformer used in transformer coupled amplifiers

Step-down Transformer

Class B Power Amplifier

Collector current flows only during the positive half cycle of the input signal.

Push-pull Principle

Amplifier uses two transistors in the circuit. One of the transistors push the current towards output during positive half-cycle of the input signal and other transistor pulls the current towards the output during the negative half-cycle of the input signal.

Crossover Distortion

Push-pull configuration, the two identical transistors get into conduction, one after the other and the output produced will be the combination of both.

Class C Power Amplifier

Collector current flows for less than half cycle of the input signal