LME 49720 questions

Artie · 10th April 2009, 07:31 PM

This segment is from the LME 49720 data sheet.

I have a couple questions:

1. On the left, the "panning" circuit. Shouldn't the plus/minus of one of those amps be reversed? Won't Vo1 and Vo2 be out-of-phase? And if so, which one? Are they using positive feedback or negative feedback?

2. On the right, the "line driver": The 49720 can sink or source 26ma. I would think that would be plenty enough for any line driver. Why the need for the additional buffer circuitry?

Thanks all. Inquiering minds want to know.

gagnou · 10th April 2009, 08:23 PM

1. The plus/minus should be reversed on the lower half of the LME 49720. Both opamps should be connected with inverting configuration. Relative attenuation is defined by the ratio of R1/(potentiometer value to ground).

2. One could use this line driver circuit as a nice class-A headphone amplifier or to drive difficult low impedance loads.

Artie · 10th April 2009, 08:31 PM

Thanks gagnou. So, it wasn't just me.

10th April 2009, 07:31 PM	#1
Artie diyAudio Member Join Date: Jul 2007	LME 49720 questions This segment is from the LME 49720 data sheet. I have a couple questions: 1. On the left, the "panning" circuit. Shouldn't the plus/minus of one of those amps be reversed? Won't Vo1 and Vo2 be out-of-phase? And if so, which one? Are they using positive feedback or negative feedback? 2. On the right, the "line driver": The 49720 can sink or source 26ma. I would think that would be plenty enough for any line driver. Why the need for the additional buffer circuitry? Thanks all. Inquiering minds want to know.

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10th April 2009, 08:23 PM	#2
gagnou diyAudio Member Join Date: May 2006	1. The plus/minus should be reversed on the lower half of the LME 49720. Both opamps should be connected with inverting configuration. Relative attenuation is defined by the ratio of R1/(potentiometer value to ground). 2. One could use this line driver circuit as a nice class-A headphone amplifier or to drive difficult low impedance loads.

10th April 2009, 08:31 PM	#3
Artie diyAudio Member Join Date: Jul 2007	Thanks gagnou. So, it wasn't just me.