Jumat, 23 Maret 2012
by skemarangkaian
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. For minimum distortion, increase the
68 ohm resistor to a point just below where
oscillation stops. A simple
buffer may be added for driving lower impedance loads.
The
output amplitude will be about
5 volts p-p but one of the
1N914’s
10k divider resistors may be changed for a different output amplitude. The circuit will work well with a
power supply voltage other than 9 volts but the
68 ohm resistor may need adjustment
Posted in:
Oscilator,
Other Circuit
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Sabtu, 02 Juli 2011
by skemarangkaian
Sometimes the need arises to construct a really simple oscillator. This could hardly be simpler than the circuit shown here, which uses just three components, and offers five separate octaves, beginning around Middle C (Stage 14). Octave # 5 is missing, due to the famous (or infamous) missing Stage 11 of the 4060B IC. We might call this a Colpitts ‘L’ oscillator, without the ‘C’. Due to the reactance of the 100-µH inductor and the propagation delay of the internal oscillator, oscillation is set up around 5 MHz. When this is divided down, Stage 14 approaches the frequency of Middle C (Middle C = 261.626 Hz).
Stages 13, 12, 10, and 9 provide higher octaves, with Stages 8 to 4 being in the region of ultrasound. If the oscillator’s output is taken to the aerial of a Medium Wave Radio, L1 may serve as the search coil of a Pipe Locator, with a range of about 50 mm. This is tuned by finding a suitable heterodyne (beat note) on the medium wave band. In that case, piezo sounder Bz1 is omitted. The Simple Oscillator / Pipe Locator draws around 7mA from a 9-12 V DC source.
Posted in:
Oscilator
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