Found in a Linear Technology documentation from the 1990s, this circuit has the voltage adjusted by resistors R1 and R2 according to the formula given in the diagram.
This circuit was found in a 1971s English magazine. We can still assemble it using BC548...
This circuit, which appears in other applications on this site, was taken from a 2000...
This circuit produces a sinusoidal signal whose frequency can be calculated using the formula next...