Chapter 11
Principles of Electronics
280
11
Multistage Transistor
Amplifiers
11.1
Multistage Transistor
Amplifier
11.2
Role of Capacitors in
Transistor Amplifiers
11.3
Important Terms
11.4
Properties of dB Gain
11.5
RC Coupled Transistor
Amplifier
11.6
Transformer-Coupled Amplifier
11.7
Direct-Coupled Amplifier
11.8
Comparison of Different Types of Coupling
11.9
Difference Between Transistor
And Tube Amplifiers
INTR
ODUCTION
INTRODUCTION he output from a single stage amplifier is usually insufficient to drive an output device.
Inther words, the gain of a single amplifier is inadequate for practical purposes. Conse quently, additional amplification over two or three stages is necessary. To achieve this, the output of each amplifier stage is coupled in some way to the input of the next stage. The resulting system is referred to as multistage amplifier. It may be emphasised here that a practical amplifier is always a multistage amplifier. For example, in a transistor radio receiver, the number of amplification stages may be six or more. In this chapter, we shall focus our attention on the various multistage transistor amplifiers and their practical applications.
T
11.1 Multistage Transistor Amplifier
A transistor circuit containing more than one stage of amplification is known as multistage transistor amplifier.
Multistage Transistor Amplifiers
281
In a multistage amplifier, a number of single amplifiers are connected in *cascade arrangement
i.e. output of first stage is connected to the input of the second stage through a suitable coupling device and so on. The purpose of coupling device (e.g. a capacitor, transformer etc.) is (i) to transfer
a.c. output of one stage to the input of the next stage and (ii) to isolate the d.c. conditions of one stage from the next stage. Fig. 11.1 shows the block diagram of a 3-stage amplifier. Each stage consists of one transistor and associated
280
11
Multistage Transistor
Amplifiers
11.1
Multistage Transistor
Amplifier
11.2
Role of Capacitors in
Transistor Amplifiers
11.3
Important Terms
11.4
Properties of dB Gain
11.5
RC Coupled Transistor
Amplifier
11.6
Transformer-Coupled Amplifier
11.7
Direct-Coupled Amplifier
11.8
Comparison of Different Types of Coupling
11.9
Difference Between Transistor
And Tube Amplifiers
INTR
ODUCTION
INTRODUCTION he output from a single stage amplifier is usually insufficient to drive an output device.
Inther words, the gain of a single amplifier is inadequate for practical purposes. Conse quently, additional amplification over two or three stages is necessary. To achieve this, the output of each amplifier stage is coupled in some way to the input of the next stage. The resulting system is referred to as multistage amplifier. It may be emphasised here that a practical amplifier is always a multistage amplifier. For example, in a transistor radio receiver, the number of amplification stages may be six or more. In this chapter, we shall focus our attention on the various multistage transistor amplifiers and their practical applications.
T
11.1 Multistage Transistor Amplifier
A transistor circuit containing more than one stage of amplification is known as multistage transistor amplifier.
Multistage Transistor Amplifiers
281
In a multistage amplifier, a number of single amplifiers are connected in *cascade arrangement
i.e. output of first stage is connected to the input of the second stage through a suitable coupling device and so on. The purpose of coupling device (e.g. a capacitor, transformer etc.) is (i) to transfer
a.c. output of one stage to the input of the next stage and (ii) to isolate the d.c. conditions of one stage from the next stage. Fig. 11.1 shows the block diagram of a 3-stage amplifier. Each stage consists of one transistor and associated