This circuit was obtained in an Electronics World of 1968. The operational amplifiers ones are types of the time, no longer used today. The circuit responds from less than 20 Hz.
Current drain with a 6 V supply is only 6 µA. Frequency is given by the capacitors, and output...
This circuit is from a Hands-On Electronics from the 90s. The integrated amplifiers used are well...
This configuration enables the use of low current switches or sensors to control high power loads...