Pspice opamp DC open loop gain

In summary, the conversation discusses using PSPICE student to work out an ideal opamp. The student has used simulation to find the gain, but is unsure how to find the DC open loop gain using the software. They have also tried to use a DC sweep to find the gain, but the results are incorrect. The conversation suggests using an open loop configuration and manually adjusting the input voltage to find the open loop gain. It also mentions using a feedback resistor and connecting terminal 1 and 5 to zero to find the offset voltage.
  • #1
hoheiho
47
0

Homework Statement


Hi, I am trying to use pspice student to work out a ideal opamp. This is what i did:
qsp3bk.png


Homework Equations


I have find out the gain for my opamp using simulation. But the problem is how can i find out the DC open loop gain using this software? i have google it and it just show me the way of "spice" to find out the open loop gain. In my courework, i need to use the simulation.

Thanks for the help
 
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  • #2
There are a lot of ways.

The easy way is to open the loop then manually adjust the input voltage until you get a finite output voltage that's not at the rails. Then take the ratio of output to input.

This is a "C" answer. There are better ways; see if you can figure one out.
 
  • #3
Thank you for your time
I am not quite understand what you mean by "that's not at the rails"?
 
  • #4
The amplifier in your diagram is "closed loop" because you have a feedback resistor of 100k from the output ( terminal 6) to the - input ( terminal 2)
Open loop means removing this feedback resistor ( the open loop gain will be very, very high !)
"not at the rails" means the output voltage is less than the power supply voltages +/- 10V ( power supply connections are sometimes called " the rails")
 
  • #5
Thanks for the info. I have simulate the open loop gain out but it seems like wrong.
waveform: http://www.sendspace.com/file/2mrn69
Do you see what is the problem with that?

I have connected a cap paralle with R2 to decrease the noise. And how can i find out the offset voltage for my opamp? It said i have to connect the terminal 1 and 5 to zero to get the offset voltage. But i am still confusing how can i do that?
 

Related to Pspice opamp DC open loop gain

1. What is Pspice opamp DC open loop gain?

Pspice opamp DC open loop gain is a simulation tool used by scientists and engineers to analyze and design operational amplifiers (opamps). It calculates the open loop gain of an opamp, which is the ratio of the output voltage to the input voltage when the feedback loop is open.

2. How is Pspice opamp DC open loop gain calculated?

Pspice opamp DC open loop gain is calculated by simulating the opamp circuit using a mathematical model and analyzing the output voltage for a given input voltage. The open loop gain is then determined by dividing the output voltage by the input voltage.

3. Why is Pspice opamp DC open loop gain important in circuit design?

Pspice opamp DC open loop gain is important in circuit design because it helps in predicting the performance of the opamp in a circuit. It allows designers to determine the stability and frequency response of the opamp, which are crucial factors in the overall performance of the circuit.

4. How can Pspice opamp DC open loop gain be used to improve circuit design?

Pspice opamp DC open loop gain can be used to improve circuit design by allowing designers to select the appropriate opamp for a given application. By analyzing the open loop gain, designers can choose an opamp with the desired characteristics such as high gain, low distortion, and wide bandwidth.

5. Are there any limitations to Pspice opamp DC open loop gain analysis?

Yes, there are some limitations to Pspice opamp DC open loop gain analysis. The simulation results may not always accurately represent the real-world behavior of the opamp due to factors such as temperature variations, component tolerances, and parasitic effects. It is important for designers to validate the simulation results with physical testing before implementing the opamp in a circuit.

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