# Why isn't this active rectifier circuit working?

I built the following active rectifier schematic on a breadboard, and inputted a 15 KHz 1V peak to peak sine wave from my signal generator.

The output looked like a sine wave and I have no idea why. Attached is the oscilloscope picture. I ran a simulation that said it would work (also attached). I know the signal was amplified correctly (on the positive swing), I could read that on the o-scope....but why wasn't it rectified?

The negative swing on the output was from 0 to -700 mV, which is the forward voltage of my diodes. Is that just a coincidence? The positive swing is from 0 to 1V. Maybe it has something to do with the simulation not accounting for real world characteristics?? Any help would be greatly appreciated.

Attached is another o-scope capture showing the input (blue) and the output (yellow). I think the phase shift is due to the amplifiers.

simulate this circuit – Schematic created using CircuitLab

• Show us a pic of your breadboard. What did you use for a power supply? Aug 28, 2019 at 1:23
• I added the breadboard picture above. For a power supply I used a 12V input from a AC->DC converter with a 9V rectifier and an inverter for +-9V to feed the amplifier rails. Aug 28, 2019 at 1:33
• Could you elaborate a little on this inverter? Have you actually measured the +9V & -9V supply rails? And the R1 on your breadboard looks suspiciously like a 10k, not a 1k - maybe it's just the lighting ... Aug 28, 2019 at 1:44
• Well I feel like an idiot, that worked! Guess I was staring at it too long and looked right over it. Interesting that a 10K in place of R1 would cause that behavior though.....I wonder if the math works out...... Aug 28, 2019 at 2:29
• Just finished up the math, and having a 10K resistor at R1 in my circuit yields the exact results I found on my oscilloscope. It just messes with the summing amplifier in the second amplification stage. Aug 28, 2019 at 3:07