Generating Stable Voltage For Multiple Applications

Focus:

This article explains the functional differences between reference diodes (zener diodes), voltage references, and voltage regulators. The benefits and drawbacks of each are discussed. For reference diodes, discussion includes the impact of operating current on temperature coefficient and specified impedance, and how power supply ripple rejection (PSRR) is calculated. Kent Walters' innovation of combining a current-limiting diode with a temperature-compensated zener diode to generate a voltage reference that is accurate over a wide input voltage range and wide temperature range, and its improved PSRR are discussed. Use of a transistor or op amp to buffer a voltage reference, buffer benefits (such as wider output current range and adjustable output voltage) and drawbacks (such as introduction of a feedback loop with potential for instability and degraded PSRR) are discussed. Three-terminal voltage regulators are described including what functions they include, their characteristics and how they compare with voltage references.

What you’ll learn:

• How to understand the differences between reference diodes, voltage references and voltage regulators when seeking to generate a stable voltage

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Author & Publication:

Steve Sandler, AEi Systems LLC, 5933 West Century Blvd., Suite 1100, Los Angeles, CA 90045, Defense Electronics, Mar 09 2010

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