When we need to build an 18V DC power supply circuit. For a transistor pre tone control. It will have a quality sound. If we use a stable DC voltage regulator.
We have many circuits to builds. But now we like the 18V DC power supply circuit using IC-7818. Because it is so well circuit, small size so fast to build, sometimes we can assemble them on a breadboard. And cheap we like it!
The IC-7818 or LM7818 or L7818 is a circuit’s key. It is a fixed DC voltage regulator IC that so popular. Since they have a low load regulation so low noise signal on our audio system.
The working principle
As we build this circuit put on the power amplifier. So The output terminal of the transformer is our AC voltage input. The proper AC input range from 18V to 22V.
You may use the 18VAC 1A transformer. It makes an output current of 1A.
Then, the AC voltage passes through a full-wave bridge rectifier (D1 through D4). They will rectify the AC into pulsating DC.
Next, the 1,000uF 35V- capacitor will filter a pulsating DC into the DC unregulated voltage. Which this voltage about 24V to 26V.
If the output current is not full to 1A. You may add one 1000uF 35V capacitor. It can keep more current.
This DC voltage will flow through the input of 3-terminal IC1. It will converter any DC voltage to stable +18 volts regulated.
The 470 uF 35V capacitor filter DC voltage to smooth better.
Now, we have the stable regulator of 18V DC power supply for a lot of application next times.
Although the IC has good circuit protection. We have to use the IC1 with a suitable heatsink because while it is working with the high current it so heats.
Parts list we need it
IC1: LM7818 or L7818_18V voltage regulator
C1: 1000uF 35V_Electrolytic Capacitors
C2: 470uF 35V_Electrolytic Capacitors
D1: D4: 1N4007_1000V 1A Silicon Diode
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