Filament source (T398E)

Despite being transistorized, this is a constant current source circuit for 1 V valve filaments such as the 1H4 tube.

S meter (CB1439E )
This S-meter circuit was found in a 1976 publication. The circuit is used to measure the signal...
Magnetic Phonocaptor Preamplifier (CB16663E)
Several versions of this circuit can be found on this website. This makes use of FETs that can...
Frequency Modulated Siren 555 CMOS (CB15868E)
With the circuit shown in the figure we have a frequency modulation which is produced by a...