The circuit given below is a variable positive voltage reference supply.The reference voltage can be set to precise values by R2.Basically the circuit is a DC amplifier based on op-amp uA 741.The negative feedback is given via the zener diode.
Circuit diagram with Parts list.Notes.
- Assemble the circuit on a good quality PCb or common board.
- Mount the IC1 on a holder.
- The POT R2 can be used for adjusting the output voltage.
- The formula for determining the output voltage is Vout= Vz [(R1+R2)(R1) ]; where Vz is the zener voltage.