Strange Experience with NE5532

Workhorse · 2nd March 2004, 10:15 AM

Hello everybody!

I recently met with a strange experience with NE5532 dual opamp.
I have got these opamps from Phillips as well as Texas Instruments.

The problem is that when these 2 half opamps are cascaded to form 2 non- inverting stages the opamp from Texas starts severe oscillations whereas Phillips make doesn't show any sign of oscillations.
CAN ANYONE TELL ABOUT THIS BEHAVIOUR?

With Regards
AmpMAN

dmfraser · 2nd March 2004, 04:17 PM

Are you bypassing the supply pins to ground with .01 to .1 µFd capacitors. If not, do it. On every op-amp package. Always.

thylantyr · 2nd March 2004, 05:03 PM

/joke

Reminds me of a recipe given to two chefs, they both
cook the food but both dishes don't quite taste the same.

Workhorse · 5th March 2004, 12:30 PM

Quote:

Originally posted by dmfraser
Are you bypassing the supply pins to ground with .01 to .1 µFd capacitors. If not, do it. On every op-amp package. Always.

I have bypassed the supply lines , but it doesn't stop oscillating.

Regards
AmpMAN

hunter audio · 5th March 2004, 02:31 PM

hi ampman

try the decoupling i think it may fail

it could be the pcb layout , but cannot think how the philips worked and the texas didnt

is it heating up too much ? or spurious wave forms are being generated (tracked by your scope)

neways take care

suranjan

Andypairo · 5th March 2004, 02:41 PM

Also Federico Paoletti, formerly designer of italian brand Audio Analogue, reported a difference between Philips and TI NE553x opamps... in his case TI was better, but IMHO it depends on the circuit you're using it into.

Link: http://www.pi.infn.it/~federico/donizetti.htm

Cheers

Andrea

6th March 2004, 07:22 PM

You didn't mention the gain settings in your circuit, but as far as I know NE553x are only stable for v>3, although Mr. Self states that the 5532 is internally compensated for unity-gain stability:
http://www.dself.dsl.pipex.com/ampins/webbop/5532.htm

Maybe thats a clue (different brands handling this feature in a different way)?

Regards

sreten · 6th March 2004, 07:31 PM

Quote:

Originally posted by Vek
You didn't mention the gain settings in your circuit, but as far as I know NE553x are only stable for v>3, although Mr. Self states that the 5532 is internally compensated for unity-gain stability:
http://www.dself.dsl.pipex.com/ampins/webbop/5532.htm

Maybe thats a clue (different brands handling this feature in a different way)?

Regards

Dual op-amps are compensated for unity gain as they do
not have the connections for a compensation capacitor.

Or they are specified to be used above a minimum gain.

The single version is compensated for gains above x3 and
has connections for a capacitor for unity gain compensation.

The dual version does not and is internally stabilised for unity gain.

Incidently the single version uses both of the dual versions
parallel input transistor arrays, this why it has better noise
performance than the dual op-amp.

sreten.

6th March 2004, 07:54 PM

Quote:

Originally posted by sreten

Incidently the single version uses both of the dual versions
parallel input transistor arrays, this why it has better noise
performance than the dual op-amp.

sreten.

Something I learned today...

Thanks for this info!

Regards

malloryn · 8th March 2004, 08:22 PM

Do you have any resistance between the output and the scope cable?

The capacitance of the cable loading the output can cause oscillation when in unity gain. When I see this it's usually about 5 MHz.

Putting a 100R in series with the output may solve your problem.

Another thing I've seen is oscillation with the supply wires seperated - twisting them together solves this.

2nd March 2004, 10:15 AM	#1
Workhorse diyAudio Member Join Date: Dec 2004	Strange Experience with NE5532 Hello everybody! I recently met with a strange experience with NE5532 dual opamp. I have got these opamps from Phillips as well as Texas Instruments. The problem is that when these 2 half opamps are cascaded to form 2 non- inverting stages the opamp from Texas starts severe oscillations whereas Phillips make doesn't show any sign of oscillations. CAN ANYONE TELL ABOUT THIS BEHAVIOUR? With Regards AmpMAN __________________ It's a fruitless endeavor to try and educate a fool that rejoices in ignorance

2nd March 2004, 04:17 PM	#2
dmfraser diyAudio Member Join Date: Dec 2003 Location: Orange County, CA	Oscillation Are you bypassing the supply pins to ground with .01 to .1 µFd capacitors. If not, do it. On every op-amp package. Always. __________________ Dan Fraser

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2nd March 2004, 05:03 PM	#3
thylantyr diyAudio Member Join Date: Feb 2001 Location: Mars	/joke Reminds me of a recipe given to two chefs, they both cook the food but both dishes don't quite taste the same.

5th March 2004, 02:31 PM	#5
hunter audio diyAudio Member Join Date: Dec 2003 Location: calcutta	hi ampman try the decoupling i think it may fail it could be the pcb layout , but cannot think how the philips worked and the texas didnt is it heating up too much ? or spurious wave forms are being generated (tracked by your scope) neways take care suranjan

5th March 2004, 02:41 PM	#6
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	Also Federico Paoletti, formerly designer of italian brand Audio Analogue, reported a difference between Philips and TI NE553x opamps... in his case TI was better, but IMHO it depends on the circuit you're using it into. Link: http://www.pi.infn.it/~federico/donizetti.htm Cheers Andrea

6th March 2004, 07:22 PM	#7
Vek Guest	You didn't mention the gain settings in your circuit, but as far as I know NE553x are only stable for v>3, although Mr. Self states that the 5532 is internally compensated for unity-gain stability: http://www.dself.dsl.pipex.com/ampins/webbop/5532.htm Maybe thats a clue (different brands handling this feature in a different way)? Regards

8th March 2004, 08:22 PM	#10
malloryn diyAudio Member Join Date: Feb 2004 Location: swindon	Do you have any resistance between the output and the scope cable? The capacitance of the cable loading the output can cause oscillation when in unity gain. When I see this it's usually about 5 MHz. Putting a 100R in series with the output may solve your problem. Another thing I've seen is oscillation with the supply wires seperated - twisting them together solves this.

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