Minggu, 12 Maret 2017
In general, electronic circuits using tubes or transistors require a source of d.c. power. For ex-ample, in tube amplifiers, d.c. voltage is needed for plate, screen grid and control grid. Similarly, the emitter and collector bias in a transistor must also be direct current. Batteries are rarely used for this purpose as they are costly and require frequent replacement. In practice, d.c. power for electronic circuits is most conveniently obtained from commercial a.c. lines by using rectifier-filter system, called a d.c. power supply.
The rectifier-filter combination constitutes an ordinary d.c. power supply. The d.c. voltage from an ordinary power supply remains constant so long as a.c. mains voltage or load is unaltered. How-ever, in many electronic applications, it is desired that d.c. voltage should remain constant irrespec-tive of changes in a.c. mains or load. Under such situations, voltage regulating devices are used with ordinary power supply. This constitutes regulated d.c. power supply and keeps the d.c. voltage at fairly constant value. In this chapter, we shall focus our attention on the various voltage regulating circuits used to obtain regulated power supply.