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Nuts & Volts Magazine (January 2013)

Build an Inverting DC-DC Converter

By Jim Stewart    View In Digital Edition  

Ever need negative voltage when all you can get is positive? This voltage mirror device will give you -V out when you put +V in, and works over a range of voltages without adjustment.


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Possible Problem with Diode D1

The Schottky diode designated D1 in the Inverting DC-DC converter may cause the output voltage to vary outside the +/- 2% specified tolerance. Schottky diodes have a higher reverse-bias leakage current than do standard diodes such as a 1N4001. Since D1 is connected to a high-impedance point on CMOS op-amp IC1, any leakage current would change the set-point of the comparator.

Diode D1 was included in the design just to clamp the input to IC1 in case a circuit failure drove the output too far negative. However, such a failure is highly unlikely. So it is recommended that diode D1 not be installed when building the kit.




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