The circuit shown is from 1994 National Semiconductor documentation but can be implemented with more modern operational amplifiers. The power supply must be symmetrical.
We found this circuit in an English documentation from 1979. It shows how you use a 100 uA...
This circuit for high-impedance magnetic headphones was suggested as an experimental amplifier for hearing...
This circuit was found in a 1987 publication. A 4017 sequentially counts time in steps set by...