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[SOLVED] Quiescent Output Voltage

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isaacnewton

isaacnewton

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The attached is a schematic of a simple op amp. I have question about the Quiescent Output Voltage of this op amp (open loop) or the Base voltage of Q6. How to calculate it by hand. It looks like the quiescent output voltage of this op amp is not well controlled.

Thank you in advance.
 

Your understanding is correct: the base of Q6 is the high impedance node of the Opamp whose voltage level can not be well controlled (open loop wise). As a matter of fact, any small current imbalance between the upper PNP and lower current sink would result in large excursion of this output node voltage.
 

you can't use a high gain amplifier in open loop operating mode.

it will saturate quickly.

to control output voltage, you must use negaive feedback

to construct amplifier into inverting amplifier or

noninverting amplifier.


best regards




isaacnewton said:
The attached is a schematic of a simple op amp. I have question about the Quiescent Output Voltage of this op amp (open loop) or the Base voltage of Q6. How to calculate it by hand. It looks like the quiescent output voltage of this op amp is not well controlled.

Thank you in advance.
Click to expand...
 

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