This circuit works as a booster operating with signals from 1 to 30MHz. The gain is between 1 and 20dB. The circuit is from the 1990 edition of Radio Electronics Experimenter magazine.
This circuit detects the presence of a pilot flame in heating systems by the presence of infrared...
In the figure we have a circuit that uses unusual components, being indicated for low frequency...
Found in older Signetics documentation, this circuit generates signals from 30 Hz to 25 kHz....