The -12 volt power supply

The power supply shown in the above schematic diagram uses a Zener diode as the main regulating device, to maintain a constant output voltage in spite of changes in input voltage. The type 1N4742A diode is rated at 12 volts, with a power dissipation limit of 1 watt. Since we want to be able to deal with load currents of at least 100 mA and possibly more, we cannot use the Zener diode by itself. (Under no-load conditions, the Zener diode would have to handle that 100 mA, which would result in a power dissipation of 1.2 watts. This would overheat and destroy the diode in short order.) Therefore, we add a power transistor as the main current-handling device for the power supply. The TIP42 PNP silicon transistor (available from Radio Shack) is rated to carry up to 10A collector current and a power dissipation of 65 watts.

Parts List

To construct and the -12 volt power supply circuit, you will need the following parts:

    • (1) 2.2, ¼-watt resistor (red-red-gold). 
    • (1) 10K, ¼-watt resistor (brown-black-orange). 
    • (1) .01µf (or larger) disc capacitor. 
    • (1) 10µf (or larger) 35 volt electrolytic capacitor. 
    • (1) 2200µf (or larger) 35 volt electrolytic capacitor. 
    • (2) Silicon Rectifier Diodes. 
    • (1) 1N4742A 12 volt Zener diode. From a two-pack available from Radio Shack. 
    • (1) PNP silicon power transistor. The TIP42 sold by Radio Shack is quite suitable here, and will be used as the example. 
    • (1) 2N3906 or 2N4126 PNP silicon transistor. Radio Shack sells a package of 15 PNP transistors that will perform well here, and provide transistors for experimental circuits as well.

About mohamad jusuf

Drs. Mohamad Jusuf Guru SMK Negeri 5 Surabaya Jl. Prof.Dr.Moestopo 167-169 Surabaya Ph.031 593488
This entry was posted in Amplifier, Antena, electronic component, inverter, Kapasitor, multivibrator, Ohm Law, pemancar TV, power supply, Radio, resistansi, resistor, stereo headphone, Televisi, transformer, Transistor, Transmissi, video. Bookmark the permalink.

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