28 Jun 2006 Nic   » (Master)

June 26th, 2006

So it turns out the voltage doubler circuit wasn't perfect either. When the multivibrator capacitors were small (0.1MFD) for some reason it made the output stage transistors overheat. If the 47MFD capacitors were removed, they did not overheat. I imagine the problem was caused by some sort of voltage spike from the capacitor, but it only mattered at high frequencies. This may be a problem with the new circuit also. Another problem with the old circuit was that the output voltage was actually about three volts less than twice the input voltage. I haven't tested this circuit, but the new output stage should get the voltage within a fraction of a volt of twice the input voltage.

Notice the difference in the output stages between the two circuits - I switched the position of the NPN transistor and PNP transistor. The old version was fail-safe; it was impossible for both transistors to be on at once. With this system, however, I had to choose four resistors to create a voltage divider that would ensure that only one of the transistors was on at once. If the input voltage is above 15V, the voltage divider no longer does this, and both transistors will turn on which will short negative to positive and melt the transistors. The benefit of this output stage is the much larger range in voltage.

Go to http://www.craterfish.org/teamprodigies/?pictures?2006/Jun to see the new voltage doubler circuit!

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