Rectifiers, Regulators and Voltage References

Abstract

A rectifier is a nonlinear circuit which converts a periodic input into a dc output. In effect, it is an ac-to-dc converter. The dc output is proportional to the peak magnitude of the input’ signal.’ In its simplest form, a rectifier is a diode peak detector with the time constant of the filter chosen as large as economically feasible. The schematic diagram of a typical rectifier which may serve as the power supply for small electronic applications, such as desktop calculators, radios, etc., is shown in Figure 15.1a. A small transformer reduces the input voltage of V _i , which in this country is usually a 117V(rms) = (117)(1.41) = 165V zero-to-peak, 60-cycle line source to a peak voltage V _in ≅ 10 volts. The effective turns ratio of the transformer is then approximately 165/10 = 16.5. The diode may have a peak forward current rating of about 1 mA and a peak inverse voltage rating of 50V. A capacitor, small in physical size, but large in capacitance (typically 2200µF with a peak voltage rating of 10V), is the remaining internal circuit element in the power supply. A load resistance supplied by the application is necessary to achieve the proper operation of the rectifier.