This circuit has an automatic dynamic gain control in a range of 6 dB to 40 dB. We found it in documentation from the 90s. The bipolar transistor is a general purpose type.
The amplifier shown in the figure is indicated for operation with resistive transducers such as...
This circuit, obtained in a 1994 documentation, uses an SCR in a relaxation oscillator to raise the...
Found in Linear Technology documentation, this circuit drains only 70 uA of the monitored circuit....