I have a circuit that outputs a voltage of -10V to +10V. Then I needed to get all values as positive output voltages from 0V to 10V i.e. I absolute the negative voltage outputs.So, I searched online and got a an "op-amp absolute value amplifier circuit with one diode" from the following links:
Circuit Simulation : http://www.cirvirlab.com/simulation/op_amp_abs_value_ampl_with_one_diode_online.php
So, I rigged up the circuit as shown in the figure with the following components and values:
Op-amps - OP177 (Analog Devices) R1 = R2 = 1k R3 = 2k Vcc = +10V and -10V Diode = IN4007
How I tested:
First I gave a Vin = 5V, for which I got around approx 2.2V output and as I varied the Vin from 5V to around 7V, the output varied from 2.2V to around 3.6V approx.
Then, second, I gave an input voltage, Vin = -5V, for which I got a very low negative output value of -0.8V.
The problem is, I am not getting the absolute output voltage and getting lower output voltages compared to Vin.
I have attached an image of the circuit digram and IC. Please help me figure out what I am doing wrong, is it with the component values? or anything else.Thanks in advance.