Archive for the 'Schematics' Category

FM Transmitter Circuit

Friday, May 23rd, 2008

Normally the capacitor in the tank circuit would connect at the base of the transistor, but at VHF the base emitter capacitance of the transistor acts as a short circuit, so in effect, it still is.

Two Transistor Wien Bridge Oscillator

Sunday, January 27th, 2008

A high gain transistor like the MPSA-18 for the first transistor will allow a much larger value for R, up to 1 Megohm. The circuit should draw between 18 and 45 mA, a value determined by the transistor gain and the value of R.

Audio Phase Shift Oscillators

Friday, January 25th, 2008

Here is a phase-shift audio oscillator with excellent distortion characteristics thanks to “softened” diode limiting provided by the 1N914 and resistor divider and degenerated gain provided by the 68 ohm emitter resistor.

Crystal Radio (and other purpose) Audio Amplifier

Wednesday, January 23rd, 2008

The TL431 is available in a TO-92 package and it looks like an ordinary transistor so your hobbyist friends will be impressed by the volume you are getting with only one transistor and the amplifier may be used for other projects, too.

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