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Circuit 124: Voltage quadrupler with moving-coil instrument
Setup information
Install the two transistors, the two diodes, the four electrolytic capacitors and the transistor as shown in
Fig. 2.124. Finally, insert the nine jumper wires. Check the placement on the board again.
If you are familiar with the relevant safety guidelines as per VDE and know how to observe them when
working with devices that are to be connected to the mains, you can now connect the transformer.
Experiment
If everything is wired correctly, you can safely go ahead and connect a low-power AC voltage source. Ide-
ally, this is the output of an audio amplifier, which reproduces a sine wave – the frequency is uncritical and
should be between 50 Hz and 400 Hz. Output voltage: 2 V. The needle of the moving-coil meter is clearly
in motion. If you check again using a multimeter, you will see that the voltage at the output is about 7 V
DC. Now you know how easy it is to quadruple the value of an AC voltage. The two transistors are used to
replace the diodes. The circuit works also with four (identical) silicon or Schottky diodes.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.124.
Components required:
2 x 2N3904 transistors,
2 x 1N4148 silicon diodes,
1 x 22 kΩ resistor,
4 x 10 μF electro-
lytic capacitors,
1 x breadboard
Fig. 2.124: Voltage quadrupler
with moving-coil instrument
149
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