1. Diode voltage multiplier circuit (Specifically diode voltage doubler circuit). By:Engr.Irshad Rahim Memon

2.  Objective of this practical is to learn that how a diode voltage multiplier circuit can raise the amplitude of input AC signal at input to provide pulsating DC signal with higher amplitude than peak voltage of AC input signal

3.  A voltage multiplier is a specialized rectifier circuit producing an output which is theoretically an integer times the AC peak input, for example, 2, 3, or 4 times the AC peak input  Diode voltage multiplier circuits increase the amplitude of input signal “n” times, where n=2,3,4 are common multipliers.  In voltage doubler circuit value of output pulsating DC signal is almost two times the peak value of input AC signal or simply Voltage doubler is a voltage multiplier with a multiplication factor of two

4. Figure 01: Diode half wave voltage doubler

5.  The name “half wave” voltage doubler is taken from the fact that output of half wave voltage doubler is same as filtered output of half wave rectifier.  During positive half cycle of input AC signal, diode D1 is forward biased, and diode D2 is reverse biased, so capacitor C1 is charged up to voltage level of (Vp-0.7) volts as shown in figure 01(a).

7.  During negative half cycle of AC input signal diode D2 is forward biased and diode D1 is reverse biased as shown in fig01(b).  As capacitor C1 is already charged, so it will act as a battery source with voltage of -(Vp- 0.7)volts; which will be added with negative half cycle of input signal.  As 0.7 volts will be dropped across D2,so capacitor C2 will be charged up (2Vp-1.4)volts.  If diode forward biased voltage drops at D1 and D2 are neglected, then C2 will provide pulsating DC voltage of value equal to 2Vp of input AC signal.

8.  Applying KVL

10.  Voltage doublers are extensively used in television and radar equipments as an alternative to heavier, larger, and expensive transformer and rectifier arrangements, which also perform the same function as that of voltage doublers.

11.  They are AC-to-DC voltage converters used in electrical and electronic circuit applications such as in microwave ovens, cathode-ray tube (CRT) field coils, electrostatic and high voltage test equipment, etc, where it is necessary to have a very high DC voltage generated from a relatively low AC voltage. The high voltage produced by a voltage multiplier circuit is in theory unlimited, but due to their relatively poor voltage regulation and low current capability most multiplier circuits produce voltages in the range of about 10kV to 30kV with a low current of less than ten milliamperes.

13.  AC Source  2 Diodes  Breadboard  2 Capacitors  Multimeter  Connecting Wire etc.

14.  Prepare the circuit on bread board as given in figure 01.

16.  Output voltage is equal to 2Vp.