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mali13 1st September 2012 05:46 PM

just wanna ask a few questions
 
Hi im new here and I just want to ask something. I found this circuit from the AD8532 datasheet and Im having trouble trying to understand how the circuit really works (from input to the output).

can someone enlighten me on this?
why are there two outputs?
what are the functions of each amp of the circuit?
does the input require a dc or ac voltage?

this is a bal line driver btw

http://s15.postimage.org/u4c7756cr/Untitled.png

AndrewT 1st September 2012 05:51 PM

bal line driver says it.
Bal stands for balanced.
All balanced interconnections have two lines.

What you have shown is an unbal to bal circuit.

mali13 1st September 2012 05:57 PM

ah i see.
can you please explain to me how the circuit specifically works? like per block?

Arty 1st September 2012 08:06 PM

does not this supposed to turn unbalanced signal to balanced ?

jan.didden 1st September 2012 08:49 PM

The lefdt A1 is a simple buffer - it is configured for gain = 1 (inverting input conneced to output).
Then there are two A2 opamps that provide the two opposing balanced outputs (one A2 is inverting).
The right A1 sets the DC input to the two A2's to make it sit at half the supply voltage for max signal range.
Makes sense?

jan didden

mali13 2nd September 2012 03:00 AM

Quote:

Originally Posted by janneman (Post 3148506)
The lefdt A1 is a simple buffer - it is configured for gain = 1 (inverting input conneced to output).
Then there are two A2 opamps that provide the two opposing balanced outputs (one A2 is inverting).
The right A1 sets the DC input to the two A2's to make it sit at half the supply voltage for max signal range.
Makes sense?

jan didden

what do you mean about making the A2s sit at half the supply voltage for max signal range? sorry I got confused there.

and two more questions pls

I simulated the circuit in multisim and what I got at the output was two waveforms that are not identical to each other. the -vout was larger than +vout. why is that?

and Im supposed to use an AC supply here right?

thank you very much!

mali13 2nd September 2012 12:08 PM

So I tried shorting the two capacitors and what I got is an AC waveform.
Is that correct? Why does it generate an AC voltage or waveform?

Mooly 2nd September 2012 12:22 PM

The circuit as shown runs on a 5 ? and a 12 volt rail.

The output of the opamps has to sit at half supply so it can go up as well as down. So if it sits at plus 6 volts it can go up as high as 12 and down as low as zero. So you get the maximum voltage swing without either the top or bottom of the signal being clipped.

The two 100k resistors set the "mid point" and generate a 6 volt reference. This appears at the output of the right hand A1

The supplies are DC.

mali13 2nd September 2012 12:32 PM

I tried placing a DC supply at the Vin and there is no output.

AndrewT 2nd September 2012 03:15 PM

Vin is where you feed in the audio signal.
V+ & V- (or Vcc & Vee) are where you feed in the power supply.


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