This 1965 circuit uses a Philips 4068 tube to measure extremely small charges. The circuit has as indicator a micro ammeter and the transistors are of the time.
This 45 to 90 Hz hum elimination circuit was obtained from a 1980s documentation. The operational can...
This circuit is suggested by the Optoelectronics Sourcebook by Texas Instruments when AC signals...
This amplifier for a sinusoidal function generator uses a 741 integrated circuit. The circuit is...