We found this circuit in an English publication from the 1980s. The circuit uses current components and can be tuned for frequencies between 300 and 1500 Hz.
In the figure we have a practical circuit for a 50 kHz bandwidth amplifier using a photo diode as...
This circuit consists of a small inverter that can generate a few hundred volts of DC voltage...
Found in a 1967 Electronic Design, this transistorized circuit compresses and then expands a pulse....