Op Amp Circuit Analysis Question: Transfer Function and Ideal Analysis

AI Thread Summary
The discussion revolves around analyzing an op-amp circuit to determine its transfer function using ideal assumptions. The user struggles with the lack of input current due to the absence of an input resistor, complicating their calculations. Key insights indicate that the 75K resistor does not affect the circuit as it doesn't load the voltage source, and the output impedance of the second op-amp is zero. The circuit can be simplified to an inverting amplifier followed by a non-inverting amplifier, allowing for the calculation of the overall transfer function by multiplying the gains of each stage. If the ideal assumptions about the op-amps are incorrect, the analysis would require a more complex approach.
priscared
Messages
11
Reaction score
0

Homework Statement


G'day, the op-amp circuit is attached. Need to know the Transfer Function.



Homework Equations



Using Ideal analysis. In=Ip=0A, and Vn=Vp
Vo/Vi=-15

The Attempt at a Solution


I have had many attempts at it. Because We don't know the input current (no input resister) it has stumped me. As there is no point doing KCL at the first left node. I have many equations but they don't seem to link up. Obviously V1=0V. V2=(2/10)Vo. and Va/18k=-Vi/6k.
Any help greatly appreciated.
 

Attachments

  • question.jpg
    question.jpg
    14.7 KB · Views: 356
Last edited:
Physics news on Phys.org
Assume the opamps are ideal: infinite gain, zero output impedance, zero input current.

Then the 75K resistor does nothing. Vi is driven by a voltage source, so the 75K doesn't load it, and has no effect on the current into the 6K resistor. The output of the second opamp has zero ohms impedance, so whatever current goes from Vi to Vo via the 75K has no effect on the output voltage.

So all you have is an inverting amplifier followed by a non-inverting amplifier. Calculate the gains of each and multiply them and that's your transfer function.

If the assumption about opamp ideality isn't true, then things get more complicated.
 
thanks

cheers
 

Similar threads

Replies
13
Views
2K
Replies
8
Views
2K
Replies
11
Views
3K
Replies
9
Views
2K
Replies
2
Views
1K
Replies
4
Views
2K
Replies
17
Views
3K
Back
Top