User:ZyMOS/Howto build an ultra low power clock with a large period

This cicuit will allow a square wave to be generated at very low power and speed using an op-amp.

Requirmednts

 * Op-amp of your choice
 * resistors
 * capacitor
 * diode (optional

Description
A low frequency, sub-Hz, clock can be created using the lowest power op-amp avalable. The circuit can take as low as 1.8uW and a clock of 30 minutes or more with the abitity to adjust the duty cycle from below 1% to above 99%. The cicuit works by charging and discharging the capacitor making the gain of the amp go from the high voltage to the low voltege. The frequency of the ocilations is set by the resistor and capacitor time constant. f=1/2/pi/r/c
 * to change the duty cycle a diode can be placed, which will change the resistance during the high or low interval.(dependign on which direction the diode is placed). two diods can but used to increase acuracy.