This high-gain circuit was found in an American publication from the 1990s. The circuit can use general purpose transistors and powered from a source or battery.
June 2017 - Microchip's new PIC18LF67K40 8-bit microcontrollers with Flash / EE / RAM memory and...
This circuit has a type of bias called "virtual earth" providing good gain, given by R2. The...
Using a capacitor as a sensor, this circuit can detect signals from 50 MHz to 500 Hz, according to the...