This circuit was found in Texas Instruments documentation from 1968. The transistors are from that time, admitting modern equivalents. The response ranges is from 20 to 20 000 Hz.
This Siliconix circuit was found in a 1980s documentation. The coil consists of 18 turns of 22...
This circuit is suggested by RCA and is based on a dedicated integrated circuit that is the...
This circuit consists of a constant current source for charging 12 V batteries. The charge is...