This circuit was found in a documentation of the 80s, having didactic purpose. For R1 values between 10k to 1M can be used. Transistors are general purpose types.
This voltage-controlled oscillator generates signals from 0 to 1.4 kHz with the components...
This is one of the channels of an amplifier suggested by Westinghouse in 1970s documentation. The circuit...
Found in technical documentation from National Semiconductor, this circuit provides a voltage of...