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.

• 0.5v to 6v Voltage Converter
  Conventional silicon transistors just can't operate at voltages less than about 0.7v. Old germanium transistors could be used, but those are hard to find these days and most are rather large in size. Some new n-channel MOSFET devices with very low gate-source threshold voltage can operate at quite low voltages. I've been experimenting with various devices and came up with one circuit, which demonstrates how to boost the low voltage from a single solar cell to a higher voltage.

• 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.