Using an LDR as a sensor, this circuit is from the Radio Electronics magazine of December 1984. The operational amplifier is the 741 and the source must be symmetrical.
When a small air current reaches the piezoelectric sensor, a small audio signal is generated and...
This circuit, from the 1977 GE semiconductor manual, uses a unijunction transistor beyond the...
The logarithmic response of this amplifier with operational is given by the presence of the...