Single Supply Absolute Value Amplifier (2)
The rail- to- rail input and output characteristics of these CMOS op amps allow them to swing very close to their supply rails–+5V and ground. By forcing U1 to operate as an inverting amplifier when the input voltage is negative (by the “ideal clamp” circuit of U2 and D1) and allowing it to operate as a normal noninverting amplifier when the input voltage is positive, op amp U1 acts like a perfect rectifier. This design can be biased above ground, handy in single supply circuits referenced to V+/2. This absolute value amplifier has unity gain an input range of within a few mV of -5V to +5V. For a faster amplifier, use an OPA354 for U1 & U2 and a small Schottky diode for D1. The dual amplifier versions, OPA2364 or OPA2354 can also be used. (Circuit is created by David Jones & Neil P. Albaugh, TI- Tucson)
Single Supply Absolute Value Amplifier (2) circuit:
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Michael Koltai
www.tina.com