Principles of Transistor Circuits, 9th Edition

Chapter 6

Bias and d.c. stabilisation

Bipolar transistors

Introduction

It is usual to begin the design of a bipolar transistor amplifying stage by choosing a value of mean collector current which enables the required current swing and/or voltage swing to be delivered with an acceptable degree of linearity. The next step is to devise a biasing circuit to give this particular value of mean collector current.

The most obvious way of biasing a bipolar transistor is by the simple circuit of Fig. 6.1 in which a resistor R_b is connected between the base of the transistor and source of steady voltage V_bb. Certainly it is possible by adjustment of R_b and/or V_bb to set the mean collector current at the desired value but such adjustments to individual transistors ...