# 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:

## Online Simulation of the “Single Supply Absolute Value Amplifier (2)” Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

and analyze the circuit, or watch our tutorial video!

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com

# Simple Absolute Value Amplifier

The rail- to- rail output characteristics of these CMOS op amps allow them to swing very close to their negative supply rails–ground. By using a non-inverting amplifier U1 to swing only positive (due to its not being capable of swinging below ground), this op amp acts like a perfect rectifier. For positive inputs, the input to the inverting amplifier U2 sees a voltage that is equal to the voltage on its non-inverting input (from follower U1), therefore the net gain of U2 is +1V/V. For negative inputs, the + input to the inverting amplifier U2 sees a voltage that is as close as U1 can swing to its negative supply rail (ground); therefore the net gain of U2 is -1V/V. This output of U1 is amplified by the noise gain of U2 and appears as an offset error on the output of the absolute value amplifier. This is the primary limitation to accuracy with very small input signals.This absolute- value amplifier has a gain of +1V/V and has an input range of +/- a few mV to -10V to +10V. (Circuit is created by Thomas Kugelstadt & Neil P. Albaugh, TI – Tucson)

Simple Absolute Value Amplifier circuit:

## Online Simulation of the “Simple Absolute Value Amplifier” Circuit

The great feature of the TINA circuit simulator that you can analyze this circuit immediately with TINACloud the online version of TINA. Of course you can also run this circuit in the off-line version of TINA.

Click here to invoke TINACloud and analyze the circuit, or watch our tutorial video!

You can send this link to any TINACloud customers and they can immediatelly load it by a single click and then run using TINACloud.

Michael Koltai
www.tina.com