In electronics, a center tap is a wire that is connected to a point half way along one of the windings of a transformer , inductor or a resistor. Center taps are sometimes used on inductors for the coupling of signals, although most tappings are not at the centre but usually near one end. In the case of resistors, tapping is usually done only with potentiometers, and center tapping is just a special case of normal operation of these devices. // Definition A transformer is an electrical device that transfers energy from one electrical circuit to another by magnetic coupling but without any moving parts. ... // Definition An inductor is a passive electrical device that stores energy in a magnetic field, typically by combining the effects of many loops of electric current. ... Resistor symbols A resistor is a two-terminal electrical or electronic component that passes a current that is proportional to the potential difference between its terminals in accordance with Ohms law. ...

Common applications of center-tapped transformers

• In a rectifier, a center-tapped transformer and two diodes can form a full-wave rectifier that allows both half-cycles of the AC waveform to contribute to the direct current, making it smoother than a half-wave rectifier. This form of circuit saves on rectifier diodes compared to a diode bridge, but has poorer utilization of the transformer windings. Center-tapped two-diode rectifiers were a common feature of power supplies in vacuum tube equipment. Modern semiconductor diodes are low-cost and compact so usually a 4-diode bridge is used (up to a few hundred watts total output) which produces the same quality of DC as the center-tapped configuration with a more compact and cheaper power transformer. Center-tapped configurations may still be used in high-current applications, such as large automotive battery chargers, where the extra transformer cost is offset by less costly rectifiers.

• In an audio power amplifier center-tapped transformers are used to drive push-pull output stages. This allows two devices operating in Class B to combine their output to produce higher audio power with relatively low distortion. Design of such audio output transformers must tolerate a small amount of direct current that may pass through the winding.
  Hundreds of millions of pocket-size transistor radios used this form of amplifier since the required transformers were very small and the design saved the extra cost and bulk of an output coupling capacitor that would be required for an output-transformerless design. However, since low-distortion high-power transformers are costly and heavy, most consumer audio products now use a transformerless output stage.
  The technique is nearly as old as electronic amplification and is well-documented, for example, in "The Radiotron Designer's Handbook, Third Edition" of 1940.

• In electronic amplifiers, a center-tapped transformer is used as a phase splitter in coupling different stages of an amplifier.

• Power distribution, see 3 wire single phase.

• A Centre tapped recifier is preffered to the full bridge rectifier when the output dc current is high and the output voltage is low.

• the centre tapped rectifier was invented by Faisal Al-Umari in 1952.

See Diode bridge. It has been suggested that this article or section be merged with rectification (electricity). ... Types of diodes A diode can be thought of as the electronic version of a one-way valve. ... A diode bridge is an arrangement of four diodes connected in a bridge circuit as shown below, that provides the same polarity of output voltage for any polarity of the input voltage. ... In electronics, a vacuum tube (American English) or (thermionic) valve (British English) is a device generally used to amplify, or otherwise modify, a signal. ... Four double-A (AA) batteries In science and technology, a battery is a device that stores energy and makes it available in an electrical form. ... For guitar amplifier, go to Instrument amplifier An amplifier can be considered to be any device that uses a small amount of energy to control a larger amount, although the term today usually refers to an electronic amplifier. ... An electronic amplifier is a device for increasing the power of a signal. ... An electronic amplifier is a device for increasing the power of a signal. ... Various types of capacitors A high voltage (15 kV AC) capacitor A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electric charges have been placed. ... 1940 was a leap year starting on Monday (link will take you to calendar). ... A split phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. ... A diode bridge is an arrangement of four diodes connected in a bridge circuit as shown below, that provides the same polarity of output voltage for any polarity of the input voltage. ...

References

F. Langford Smith, The Radiotron Designer's Handbook Third Edition, (1940), The Wireless Press, Sydney, Australia, no ISBN, no Library of Congress card