This proximity sensor was found in a 90s Popular Electronics. The base is a PLL567 that operates at around 100 kHz. The circuit operates by capacitance sensing.
This configuration with the LM383 appears elsewhere on this site. The circuit shown was obtained...
This signal attenuator was suggested by Electronics Now magazine in April 1999. The circuit is...
The voltage gain of this DC amplifier is 100 times, given by the relationship between R2 and R1....