Home > Circuit Bricks > Voltage Reference - Fixed
UPDATED:.22:45 02 September 2009
FUNCTION BLOCK
DESCRIPTION
  • This voltage reference provides a fixed voltage level regardless of changes in the supply voltage.
  • This uses a Zener diode in a potential divider.
CIRCUIT DETAILS
  • This is a simple way of clamping a voltage (keeping at a steady level) regardles of the input.
  • It is useful for accurate DAC (Digital to Analogue Converters
  • This can also be used to regulate low current supplied to a circuit. Add a Current Amplifier and you have a basic regulated power supply.
Input

Circuit Diagram
"Vin" should be about 3 to 10 volts above the voltage you want.
Output

Choose a Zener diode at the voltage you want as an output - "Vout" - note it is Reverse Biased!

R1 can be calculated exactly but generally 470 ohms should work for most voltages.

The capacitor helps to stabalise the output voltage.

DEVICE DETAILS
Cathode

Anode

Zener diodes look very similar to signal diodes. They are both made of glass, and also have a black band to denote the cathode.
300mW zener
Written by Phil Townshend - 2008
www.edutek.ltd.uk - Working Electronics For Students & Teachers