9VDC Power Supply using Zener and Transistor
This 9VDC power supply using zener and transistor can be used to power circuits or electronic devices that would normally use a 9 volt battery, saving us the cost of the battery while being used at home.
To better understand the operation of this 9VDC voltage source, it is recommended to first read the following tutorial: Voltage regulator with zener diode. This 9VDC voltage source is very simple and can be assembled in very little space.
How the 9VDC Power supply works?
The main components of this circuit are a zener diode, which is used as a voltage reference and a bipolar transistor to amplify the current that is delivered to the load. The transformer and rectifier diodes allow an unregulated voltage to be obtained at the electrolytic capacitor terminals of approximately 16.5 volts.
With a 10 volt zener diode connected to the base of the transistor, an output voltage is obtained at the emitter of the transistor: Vout = Vz – Vbe = 10V – 0.6V = 9.4 VDC.
Also included is an LED that indicates when the power is on. Although the transistor used allows a maximum current of 1 ampere, it is recommended that the current is not greater than 500 mA.
List of the 9VDC Power Supply components
- 1 transistor NTE128 or similar (Q1)
- 1 1/2 watt 10V zener diode (Z)
- 2 diodes 1N4001 or similar (D1, D2)
- 1 red or green LED (D3)
- 1 150 ohm resistor, 1 / 2W (R1)
- 1 680 ohm resistor / resistor, 1 / 4W (R2)
- 1 electrolytic capacitor 2200uF / 25V or more (C)
- 1 120/240VAC to 24VAC center tapped transformer, 500mA (18V transformer can be used with no problems) (T1)