The design of direct voltage and current stabilizers using semiconductor devices

The design of direct voltage and current stabilizers using semiconductor diodes and transistors is discussed, and a design procedure is given. The basic circuit considered is that in which a control element is placed in series with the supply and the load. The voltage across, or the current through, the load is compared with a reference and the difference is used to control the voltage drop across, or the current flowing through, the control element. The control is effected so as to keep constant the voltage across, or the current through, the load. Methods of achieving high stability against changes in input (or supply) voltage and changes in load are described. The effect of changes in ambient temperature on the output is considered and methods of minimizing this are given. Other factors considered are the transistor parameters which affect the degree of stabilization and limit the load current and/or voltage, and the response of the stabilizers to sudden changes in load. The design of a suitable power supply to enable the stabilizers to be used with a.c. mains is mentioned. The silicon junction diode operated in the Zener breakdown region is used as the reference element. Its properties and use as a voltage reference are discussed, including methods of reducing the temperature coefficient. The power-handling capabilities of the conventional series stabilizer are limited by the dissipation of the series transistor. The possibility of using non-dissipative regulator circuits is considered.