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single supply operation of instruementation amplifier

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waqas5304

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can anyone help'
i am using three TL074 opamps to make a pre amplifier for low impedance microphone.it works fine with dual supply but when i try to operate it with single supply it does not work. i have tried many things but of no use.can anyone help me
 

IanP has replied to your previous post and suggested the use of a bias circuit, because you are not biasing the inputs of the opamps connected to the microphone.

Try that circuit, it should work.
 

hi VVV
i have tried the circuit suggested by Ianp but of no use.either i am unable to understand how the baising is to be used.kindly tell me hoe to use the circuit from diagram i can see both
+ve and -ve outputs what is Batt??
kindly help i am in trouble

Added after 58 minutes:

here is the circuit what wrong with it
7_1164079222.JPG
 

I don't think you need the fourth opamp.
You nned a divider on the (+) input of one of the input opamps. That will be one side of the microphone. Try 100k/ 100k. That wil keep the inputs of the two opamps biased. Right now the micropone is floating and so are the inputs of the opamps, which they should not be.

With the divider in place, the circuit should start to work. We will think about other problems later (noise, etc.) Try this first.
 

Another and probably the easiest option of biasing inputs is to connect >100kΩ resistors between the virtual ground and both (+) inputs ..

Regards,
IanP
 

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