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Why wont this circuit work?

andrew.grimm3

Dec 7, 2011
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Can anyone tell me why this circuit wont work? I ran a simulation and there's no gain on the output. (see attachment)
 

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duke37

Jan 9, 2011
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The op-amps have their outputs connected together, they have the inputs connected to produce opposite phase outputs so they will be fighting each other.

U1 has a negative feedback to set the operating condition, U2 does not and will likely be driven hard in one direction.
 

andrew.grimm3

Dec 7, 2011
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Ok I understand. So one op amps output phase is not the same as the other. Therefore both output phase responses of each op amp should be identical correct?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Firstly, you need to ask yourself: *Why* are you connecting 2 op-amps in parallel?" In this case the parallel connection is wrong (because the inputs of one are presumably shown reversed).

Did you design this ourself, or did it come from somewhere?
 

duke37

Jan 9, 2011
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Even if you get the phase right, you will not get quite identical outputs so there will still be an argument. A 1 ohm resistance in each output may alleviate this problem. Why not use a more powerful amp instead.

Antiphase connection is used to increase the output power without increasing supply voltage. In this case the speaker is connected between the amplifier outputs. There are dual op amps designed for this but I forget the numbers.
 

andrew.grimm3

Dec 7, 2011
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I designed the circuit myself. Im trying to build a bridge amp using (2) LM1875 IC's. I researched some on how bride amps work, and I'm still confused on what goes on. I just built this in Multisim and run a analysis so I'm looking for some help.
 
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