Op Amp Circuit Analysis Question: Transfer Function and Ideal Analysis

In summary, the conversation discusses an op-amp circuit and the need to determine its transfer function using ideal analysis. The attempt at a solution involves various equations and assumptions, but the circuit can be simplified as an inverting amplifier followed by a non-inverting amplifier. The transfer function can be calculated by multiplying the gains of each amplifier. However, if the assumption of opamp ideality is not true, the solution becomes more complex.
  • #1
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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.
 

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  • #2
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.
 
  • #3
thanks

cheers
 

1. What is an op amp?

An op amp, short for operational amplifier, is an electronic device that amplifies the difference between two input voltages. It has a high gain, high input impedance, and low output impedance, making it ideal for signal amplification and processing.

2. How does an op amp work?

An op amp consists of a differential input stage, a gain stage, and an output stage. The differential input stage compares the two input voltages and amplifies the difference. The gain stage then multiplies the amplified difference by a large factor. Finally, the output stage provides a low impedance output to drive external circuitry.

3. What are the different types of op amps?

There are several types of op amps, including inverting, non-inverting, differential, and instrumentation. Inverting and non-inverting op amps have different input configurations, while differential op amps have two inputs and provide the difference between them as the output. Instrumentation op amps have high precision and are often used in measurement and control systems.

4. How do I analyze an op amp circuit?

To analyze an op amp circuit, you can use the concept of virtual ground, which states that the voltage at the inverting input of an op amp is equal to the voltage at the non-inverting input. You can also use Kirchhoff's laws and Ohm's law to analyze the circuit and calculate the output voltage.

5. What are some common applications of op amps?

Op amps have a wide range of applications, including audio amplifiers, signal conditioning, filtering, and voltage regulation. They are also commonly used in instrumentation and control systems, as well as in electronic circuits for computers and communication devices.

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