What's the function of this?

stef1777 · 21st March 2006, 08:45 AM

Hi Folk!

I'm analysing a circuit from a pre-amplifier. I don't have the schematics. Not all component are represented on this home made diagram.

Does someone understand the use of IC400 in this circuit?

Thanks for your help.

EC8010 · 21st March 2006, 09:08 AM

It's an integrator that is performing the task of DC servo and holding the DC at the output of the second IC at 0V. Quite why they've chosen to use an OPA2134 for that function, I don't understand. The servo op-amp is usually chosen for its low DC offset rather than good audio quality.

stef1777 · 21st March 2006, 09:13 AM

Great thanks. I was thinking too for a DC servo but I was confused as they use an 2114 for the "audio signal" and an 2134 for the DC...

Do you will have a recommandation to update both opamp?

I was thinking to an AD8620B for the IC400 and 2134 (or something else) for IC403.

.

SY · 21st March 2006, 11:56 AM

Quote:

Originally posted by EC8010
Quite why they've chosen to use an OPA2134 for that function, I don't understand. The servo op-amp is usually chosen for its low DC offset rather than good audio quality.

My guess is that, the way this circuit is configured, any integrator grunge will be fed directly into the non-inverting input with no attenuation. So op-amps which are particularly suitable from a low-offset and low-bias-current standpoint might not be optimal.

stef1777 · 21st March 2006, 12:16 PM

What about AD822 for IC400?

EC8010 · 21st March 2006, 12:16 PM

Quote:

Originally posted by SY
My guess is that, the way this circuit is configured, any integrator grunge will be fed directly into the non-inverting input with no attenuation. So op-amps which are particularly suitable from a low-offset and low-bias-current standpoint might not be optimal.

Good point, I've no doubt that you are right. It's a trade-off between good DC performance and LF noise.

21st March 2006, 09:08 AM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	It's an integrator that is performing the task of DC servo and holding the DC at the output of the second IC at 0V. Quite why they've chosen to use an OPA2134 for that function, I don't understand. The servo op-amp is usually chosen for its low DC offset rather than good audio quality. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Function Generator?	TheDriver	Parts	4	18th August 2008 10:46 AM
Looking for an used function generator	Eva	Swap Meet	0	21st February 2008 07:56 AM
Amp Will Not Function	prorms	Solid State	16	2nd December 2006 09:26 PM
Why this amp does not function ?????	PicancoNet	Solid State	10	23rd January 2004 05:45 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

21st March 2006, 09:13 AM	#3
stef1777 diyAudio Member Join Date: Jun 2004 Location: Paris	Great thanks. I was thinking too for a DC servo but I was confused as they use an 2114 for the "audio signal" and an 2134 for the DC... Do you will have a recommandation to update both opamp? I was thinking to an AD8620B for the IC400 and 2134 (or something else) for IC403. .

21st March 2006, 12:16 PM	#5
stef1777 diyAudio Member Join Date: Jun 2004 Location: Paris	What about AD822 for IC400?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)