Analog designers are frequently required to develop circuits that convert high-voltage signals to levels acceptable for low-voltage data converters. This paper describes several solutions for this common task using modern amplifiers and typical power supplies. Five examples of conditioning ±10V bipolar signals for low-voltage, single-rail analog-to-digital converters (ADCs) are presented: a modular approach, a single-supply/single-part approach, and an instrumentation amplifier approach. Both single-ended, differential input versions are discussed.
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Analog front-end designers are often confronted with the challenge of coupling high-voltage bipolar signals to ADCs that operate on low-voltage single supplies. Traditional single-part, high-voltage converters are becoming obsolete, although many applications continue to use high-voltage bipolar analog signals. Modern data converters are designed on small geometry processes because of advanced digital capabilities, higher yields, and overall lower costs. Op amps, on the other hand, are designed on large geometry processes to withstand higher internal voltages and allow precise control of internal elements. Modern op amps offer several outstanding features, such as rail-to-rail I/O, a wide input common-mode voltage range, linear transfer functions, low power consumption and low-voltage operation. By using discrete op amps and data converters, designers can optimize circuit performance by using the proper part and avoiding expensive, compromised, single-part solutions.
