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<title>Relaxation Oscillator</title>
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<p>
This circuit is
an <a
href="http://en.wikipedia.org/wiki/Electronic_oscillator">oscillator</a>
that generates a <a href="http://en.wikipedia.org/wiki/Square_wave">square wave</a>. The <a
href="http://en.wikipedia.org/wiki/Operational_amplifier">op-amp</a>
starts with its two inputs in an unknown state; let's say it starts
with + slightly higher than –. The op-amp greatly amplifies
this difference, bringing its output to the op-amp's
positive power supply voltage, its maximum output (15 V in this
case). The two 100k resistors act as a voltage divider which put the +
input at half the output voltage, or 7.5 V. The – input is at
ground, lower than the + input, so the op-amp output stays at 15 V.
<p>
Current flows from the op-amp output to ground through the capacitor,
charging it. As soon as it charges to slightly more than 7.5 V, the
– input is now higher than the +, and so the output flips to -15
V. This brings the + input to -7.5 V.
<p>
Now current flows in the other direction, discharging the capacitor
and reversing its polarity until it reaches -7.5 V. Then the cycle repeats.
<p>
To hear the waveform, increase the simulation speed and press the <b>Play</b> button.
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Next: <a href="e-triangle.html">Triangle Wave Generator</a><p>
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<br>Generated Wed Dec 7 2016
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