The simple diode network can stabilize the voltage supplied to CMOS circuitry from a battery. D1 and D2 must have a combined forward-voltage drop of about 1.5 V. And D3 is an LED with a forward-voltage drop of about 1.7 V. The table shows the network`s output voltage as the battery`s voltage declines. [Link]
Diode Cmos Stabilizer Circuit Diagram
