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Ocampo oscillating how to stabilize

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Posted on December 29, 2016 at 08:16:10
jk
Audiophile

Posts: 366
Joined: October 4, 1999
 Down a bit further someone posted a question about OPA2604 op amps. I had used these before but found out the hard way that they are not internally compensated. They blew fuses because of oscillating.

My question is, can I just wire small caps in from + to ground and from negative to ground on each opamp to clear this issue ? Given the improvement it may be worth it.

 

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RE: Ocampo oscillating how to stabilize , posted on January 3, 2017 at 15:23:44
AbeCollins
Audiophile

Posts: 46302
Location: USA
Joined: June 22, 2001
Contributor
  Since: February 2, 2002


Not knowing what is causing the oscillation - design flaw, poor layout (stray capacitance), wrong opamp choice for the application, etc.

Just for grins, I would try a 0.1uF cap at -V to ground and +V to ground, as close as possible to the opamp +V and -V pins keeping all leads as short as possible.

Also, stray input capacitance can cause stability issues. Signal phase shifts can occur which may result in oscillation. The effects of stray input capacitance can be minimized with a small capacitance placed in parallel with the feedback resistor. Try 10pF. High frequency gain and noise will be reduced with a feedback capacitor.

Stray output capacitance can also cause stability problems. Placing a low value resistor (~100 ohm) in series with the opamp output will isolate it from the stray output capacitance.


 

RE: Ocampo oscillating how to stabilize , posted on January 3, 2017 at 19:34:32
jk
Audiophile

Posts: 366
Joined: October 4, 1999
 Thanks Abe, I'll try it.

 

RE: Opamp oscillating how to stabilize , posted on January 16, 2017 at 11:29:54
jk
Audiophile

Posts: 366
Joined: October 4, 1999
 Abe, thanks mate. Glad you could decipher the subject, darn auto spell takes over sometimes.

I really like the sound of the OPA2604, but it just kept blowing fuses. I will find a way to fit the caps in and give it a shot. I appreciate your help.

John

 

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