Analyzing this operational amplifier circuit with DC

In summary, the analysis of the operational amplifier (op-amp) circuit with direct current (DC) involves evaluating the circuit's behavior by applying DC voltage sources. Key parameters such as input and output voltage levels, gain, and feedback configurations are examined to determine the circuit's performance. By using techniques like nodal analysis and the principles of superposition, one can derive critical characteristics including the input and output impedance, bandwidth, and stability of the circuit. This analysis is essential for understanding how the op-amp operates in various applications, ensuring optimal functionality and design.
  • #1
ZoeDale
11
1
Homework Statement
a) Treat the operational amplifier in the circuit below as ideal and solve for Vo.
b) Treat the op amp as a non-ideal device that is powered by VCC and VEE; describe several ways in which your answer in part a) will change.
Relevant Equations
KVL; KCL;
Hi all, I attached my attempt at a solution in the attached picture. I am using the textbook titiled as ”electronic circuit analysis“ by David E. Johnson, and op amp is in chap 3;
while I did not find any example that attach the Vee and Vcc with amplifier . It seems that v+ = v- doesn’t hold in this scenario; can anybody give me some hints?

thanks!
 

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  • #2
IMG_3132.jpeg
 
  • #3
Um, that circuit has a fundamental problem, and is non-physical. SPICE, for example, would throw an error if you tried to analyze it. Are you sure this came from a textbook?
 
  • #4
this is a problem from our qualify exam samples for practice. No solutions provided. :cry:
 
  • #5
ZoeDale said:
this is a problem from our qualify exam samples TAT for practice. No solutions provided.
Well, that circuit is complete nonsense as drawn, so there is no solution to the problem. Maybe that is the test of the problem -- you are supposed to reply that the circuit is nonsense in order to get credit.

Can you say what is totally wrong about that circuit?

1701990267207.png
 
  • #6
berkeman said:
Um, that circuit has a fundamental problem, and is non-physical. SPICE, for example, would throw an error if you tried to analyze it. Are you sure this came from a textbook?
Seems that v+ can not be equal to v- in the ideal condition; or the non-ideal condition. But I can not figure out what will happen in the circuit; Can you give more hints on that? Thank you!
 
  • #7
ZoeDale said:
Can you give more hints on that?
Opamp inputs must have some DC bias connection to somewhere to supply their input bias currents and to set the DC operating point. Do you see the issue now? :smile:
 
  • #8
berkeman said:
Opamp inputs must have some DC bias connection to somewhere to supply their input bias currents and to set the DC operating point. Do you see the issue now? :smile:
oh, you mean they should be on each side of the lying triangle's waist, separately?
 
  • #9
ZoeDale said:
oh, you mean they should be on each side of the lying triangle's waist, separately?
Sorry, I don't understand your response.
 

FAQ: Analyzing this operational amplifier circuit with DC

What is the purpose of an operational amplifier in a DC circuit?

An operational amplifier (op-amp) in a DC circuit is typically used to amplify voltage, perform mathematical operations like addition, subtraction, integration, and differentiation, or to function as a buffer to isolate different stages of a circuit.

How do you determine the DC operating point of an op-amp circuit?

The DC operating point, or quiescent point, is determined by analyzing the circuit with all AC signals turned off. This involves solving the circuit equations to find the DC voltages and currents at various points in the circuit, considering the power supply voltages and any biasing resistors or sources.

What are the common configurations of op-amp circuits used in DC analysis?

Common configurations include the inverting amplifier, non-inverting amplifier, voltage follower (buffer), summing amplifier, and differential amplifier. Each configuration has specific characteristics and applications in DC circuit analysis.

How does the input offset voltage affect the performance of an op-amp in a DC circuit?

The input offset voltage is the differential DC voltage required between the input terminals of the op-amp to make the output zero. It can cause errors in DC circuits by introducing a small but significant offset in the output voltage, which may need to be compensated for in precision applications.

What role do feedback resistors play in the DC analysis of op-amp circuits?

Feedback resistors determine the gain and stability of the op-amp circuit. In a DC analysis, they set the ratio of the input signal to the output signal, thereby controlling the amplification factor. The values of these resistors are crucial for achieving the desired performance and stability of the circuit.

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