LM3875 at low gain

dsavitsk · 26th August 2006, 07:06 AM

Has anybody tried using one of these chips at low or even unity gain? Are they stable? Any thoughts or advice?

I would like to use a SRPP preamp/driver stage but the gain will be too high normally, but at low gain it should work very well -- if the chip is stable.

-d

Nuuk · 26th August 2006, 08:22 AM

No they are not stable at low gain. If you want a low gain GC, use something like the OPA541/549.

ash_dac · 26th August 2006, 09:40 AM

Hi,

In the LM3875 datasheet figure 2 they show additional compensation capacitance to reduce HF ac gain. I assume the LM3875 is compensated for gains greater than 10.

Can the LM3875 be compensated for lower gains ?

I was thinking about a LM3875 regulated-LM3875 amplifier...

edit:- never realised how sensitive these chips are...picking up fluorescent noise!

26th August 2006, 07:06 AM	#1
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	LM3875 at low gain Has anybody tried using one of these chips at low or even unity gain? Are they stable? Any thoughts or advice? I would like to use a SRPP preamp/driver stage but the gain will be too high normally, but at low gain it should work very well -- if the chip is stable. -d

26th August 2006, 08:22 AM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	No they are not stable at low gain. If you want a low gain GC, use something like the OPA541/549. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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26th August 2006, 09:40 AM	#3
ash_dac diyAudio Member Join Date: Jan 2005 Location: UK	Hi, In the LM3875 datasheet figure 2 they show additional compensation capacitance to reduce HF ac gain. I assume the LM3875 is compensated for gains greater than 10. Can the LM3875 be compensated for lower gains ? I was thinking about a LM3875 regulated-LM3875 amplifier... edit:- never realised how sensitive these chips are...picking up fluorescent noise!

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