Solving for Output Voltage of Op Amp

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Discussion Overview

The discussion revolves around calculating the output voltage of an operational amplifier (op-amp) given specific input conditions and parameters. It includes aspects of homework problem-solving, theoretical understanding of op-amp behavior, and the limitations imposed by power supply voltages.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant states the output voltage formula as Vo = A(vp - vn) and inputs values for the inverting input voltage (Vn = 4mV), open-loop gain (A = 2*10^5), and non-inverting input voltage (vp = 0V) based on the problem statement.
  • Another participant calculates the output voltage as Vo = -800V, questioning the discrepancy with the expected answer of -10V.
  • Some participants discuss the concept that the output of an op-amp cannot exceed its power supply voltages, suggesting that the output voltage is limited to a maximum of 10V and a minimum of -10V.
  • There is a suggestion that the calculated output voltage should be noted as -800V, but it will be truncated to -10V due to the power supply limits.

Areas of Agreement / Disagreement

Participants generally agree that the output voltage is constrained by the power supply limits, but there is no consensus on the implications of the initial calculation of -800V and how to properly document it in relation to the expected output.

Contextual Notes

The discussion highlights the importance of understanding the limitations of op-amp outputs in relation to their power supply, but does not resolve the confusion regarding the initial calculation and its documentation.

Who May Find This Useful

Students studying operational amplifiers, individuals interested in electronics and circuit design, and those seeking clarification on op-amp behavior in practical applications.

rzn972
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Homework Statement



What is the output voltage for an op amp whose non-inverting input is connected to ground and its inverting-input voltage is 4mv? Assume that the op-amp open-loop gain is 2*10^5 and its supply voltage is Vcc=10V

Homework Equations


Vo= A(vp-vn)


The Attempt at a Solution


The problem gives
Vn= 4mv
A=2*10^5
Vcc=10V
Since it says the non-inverting input is connected to ground, does that mean vp=0?
Vo=2*10^5(0-.004V)
Vo=-800 V
However the answer is suppose to be -10V. What am I doing wrong?
Thanks for helping!
 
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rzn972 said:

Homework Statement



What is the output voltage for an op amp whose non-inverting input is connected to ground and its inverting-input voltage is 4mv? Assume that the op-amp open-loop gain is 2*10^5 and its supply voltage is Vcc=10V

Homework Equations


Vo= A(vp-vn)


The Attempt at a Solution


The problem gives
Vn= 4mv
A=2*10^5
Vcc=10V
Since it says the non-inverting input is connected to ground, does that mean vp=0?
Vo=2*10^5(0-.004V)
Vo=-800 V
However the answer is suppose to be -10V. What am I doing wrong?
Thanks for helping!

Can the output of an op-amp ever exceed its power supply voltages (positive and negative supplies)?
 
Ahh, I see so the max Vo is 10 and min Vo is -10. So is what I did wrong? Do I have the write down that calulated vo= -800 but say the min is -10V.
 
rzn972 said:
Ahh, I see so the max Vo is 10 and min Vo is -10. So is what I did wrong? Do I have the write down that calulated vo= -800 but say the min is -10V.

That's the idea. Do the calculation and then state why in actuality the value will be "truncated" by the limits imposed by the power source.
 
Thank you so much!
 

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