Amplifier IC Generates A Negative Voltage Reference With The Fewest Parts And A Single Supply Rail

by Chapin Wong, Maxim Integrated, San Jose, Calif., How2Power Today, Dec 15 2014

Focus:
A common way to generate a negative voltage reference is to use an op amp to invert the output of a positive precision voltage reference. This approach typically requires a positive reference, the op amp, and two supply rails. Another approach uses a voltage reference in combination with a charge pump, an op amp, and a positive supply rail. In the design presented here in this brief article, this latter approach is simplified by taking advantage of a chip (the MAX9820) that combines an op amp with an integrated charge pump. The MAX9820 is actually a headphone amplifier IC, but when used to generate a negative voltage reference, enables a simple design with few parts, a small footprint, and a single supply rail. Circuit operation and component choices are explained and output voltage-versus-temperature results are shown.

What you’ll learn:

• How to generate a negative voltage reference using few components and just a positive supply rail

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