What is the purpose of this diode bridge circuit connected to an op amp's output?

Thread Starter

sp2821

Joined Jan 8, 2014
21
Hi,

I found this circuit on one of op amp's application notes and I'm not sure why there's a diode bridge at the output of an op amp.
I initially thought the diode bridge circuit acts as a clipper and will limit Vout to about +/-5V. But when I ran simulation Vout actually rose above +/-5V (although distorted).
Can anyone explain why it's there and how it exactly works?

Thank you!
upload_2017-12-15_9-11-46.png
 

Alec_t

Joined Sep 17, 2013
10,598
Can't see any obvious reason for the bridge, unless it's for gating the opamp output (by reversing the two supply rails to the bridge) to a following stage? Unlikely, though.
 

LesJones

Joined Jan 8, 2017
2,417
I think it may be producing a small dead band around zero volts output. Possibly so a control system did not hunt arround the zero output position. If you gave more information on the topic of the application note it might help.

Les.
 

crutschow

Joined Mar 14, 2008
23,782
It generates a clipped output at about 1 diode drop below the bridge supply voltages if you add a load to the output (try 50kΩ)
 

WBahn

Joined Mar 31, 2012
24,974
Hi,

I found this circuit on one of op amp's application notes
What did said application note say was the purpose of said circuit?

It's very unusual for an app note to just have a schematic without at least a meaningful name associated with it.
 

Thread Starter

sp2821

Joined Jan 8, 2014
21
What did said application note say was the purpose of said circuit?

It's very unusual for an app note to just have a schematic without at least a meaningful name associated with it.
It didn't really have much information. It was just one of many circuit diagrams in their note :(
 
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