Dave's Circuits:  Frequency to Voltage     Period to Voltage     Sine to Square Wave      Voltage Converters   
 Voltage to Frequency     DC to DC Power Supplies   High Voltage Power Supplies   
Switchmode Power Supplies  Voltage Controlled Oscillators

• 0.5V Negative Supply
  Although not very efficient, this simple circuit, consisting of two LEDs and a photo diode, generates a negative voltage with a current level of a couple milliamps.  It is ideal for supplying a negative rail to low power “rail to rail” op amp circuits, which need to have a true zero volts output.

• CHARGE PUMP EFFICIENTLY DIVIDES SUPPLY VOLTAGE
  This circuit uses a few FETs and logic devices to down convert a DC voltage to about one half its value