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• CMOS SCHMITT TRIGGER IC MAKES VCO
  By changing the supply voltage fed to a classic 4584 Schmitt trigger type oscillator, the oscillator frequency can be changed over a range of 50:1.  A 74HCU04 inverter is used at the output of the 4584 to maintain a constant TTL logic level signal.

CMOS Schmitt Trigger IC Makes VCO - By changing the supply voltage fed to a classic 4584 Schmitt trigger type oscillator, the oscillator frequency can be changed over a range of 50:1.  A 74HCU04 inverter is used at the output of the 4584 to maintain a constant TTL logic level signal. ….(designed by David A. Johnson)

Miniature Audio Oscillator - The Miniosc, low distortion battery powered audio oscillator  (added 6/07)

Minimal audio oscillators - In order to generate a single note you may try these simple circuits. With only three components you may implement some basic buzzers. You need a telephone earpiece for the first circuit. Any old telephone set has got one of those magnetic earpiece that is right for our purposes. Add an extra capacitor and a transistor and you have your buzzer. Frequency of operation is about 1800 Hz and the capacitor must be changed if you wish to have a different frequency. The second circuit .... (added 9/07)

Simple Audio Oscillator - For use with the millivoltmeter, for testing amps and speakers  (schematic added 6/07)

Variable Frequency Audio Oscillator  - Variable Frequency Audio Oscillator circuit (added 08/08/08)