Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The circuit has a flat response from 10 Hz to 700 kHz.
August 2016 - It can be obtained from Mouser Electronics new operational amplifiers with extremely low...
The output voltage of this circuit is approximately four times the supply voltage. The circuit is from...
The galena XTAL is replaced by a germanium diode in this Project. Diodes such as the 1N60 or 1N34...