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.
This circuit emits a sound at regular intervals to prevent you from falling asleep, for example. It...
November 2016 - Texas Instruments' new TLV8802 nano-power operational amplifiers for wireless...
The circuit presented is from 1994 and can be implemented with more modern equivalent components. We...