# Op Amp Design #2: Solving Vo = 3*10^4(i2-i1)

• gfd43tg
In summary, the student is trying to figure out how to solve a problem involving a difference amplifier, but is having difficulty because of incorrect labeling on his diagram and equations. He is also having trouble with a new tablet that is unable to read pdf files.
gfd43tg
Gold Member

## Homework Statement

Design a circuit containing a single op amp that can perform the following operation: Vo = 3*10^4(i2-i1), where i2 and i1 are input current sources

## The Attempt at a Solution

Where I'm at right now, I am just using the equation for a difference amplifier gains, but I have more unknowns than equations, so I don't know what to do.

#### Attachments

• 5.7 attempt 1.pdf
123.9 KB · Views: 210
Hi Maylis. Could I suggest that you post images as unadorned jpeg (or png, etc) files, so those using basic tablets (and costly data plans) are still able to participate?

Alright, here is a .png

#### Attachments

• 5.7 attempt 1.jpg
10.5 KB · Views: 412

Big hint: since the inputs are current you need a total of only 2 resistors.

Oh I see, I need to change the label of R2 and R3. Either way my problem persists. The equation should be correct now with that change, as well as making it R3*i2 in my second stop

Last edited:
Okay, I source transformed, corrected the labeling, and this is what I came up with.

Edit: my bad, I was saying that no current goes through R1 and R3, which can't be possible since there is a potential difference between Vn/Vp and the resistors. Now the equations are even messier. Where do you get the fact that I only need 2 resistors from? I am following the template for a difference amplifier as given in the textbook and I redrew as my original image, pre-source transform

#### Attachments

• 5.7 attempt 2.jpg
10.8 KB · Views: 411
• 5.7 attempt 3.jpg
11.6 KB · Views: 388
Last edited:
See if you can get it to work without R1 and R3.

NascentOxygen said:
See if you can get it to work without R1 and R3.

And RL.

And BTW the pdf file is a lot easier to read, for me anyway.

If the new tablets, iPads etc etc can't even read pdf files any more I am more po'd than ever that xp is disappearing ... we are dumbing-down at an ever-increasing rate ...

## 1. What is an op amp?

An op amp, short for operational amplifier, is a type of electronic circuit component that is commonly used in analog signal processing and amplification applications. It is designed to amplify and manipulate voltage signals in a variety of ways.

## 2. What does Vo = 3*10^4(i2-i1) mean?

This expression is known as the voltage transfer function for an op amp circuit. It represents the relationship between the output voltage (Vo) and the difference between the input currents (i2-i1). In simpler terms, it shows how changes in the input currents affect the output voltage of the circuit.

## 3. How do you solve for Vo in this equation?

To solve for Vo, we can use basic algebraic principles to manipulate the equation and isolate Vo on one side. This can then be used to determine the output voltage for a given set of input currents.

## 4. What factors affect the voltage transfer function of an op amp circuit?

There are several factors that can affect the voltage transfer function of an op amp circuit, including the op amp's gain, input and output impedance, and the values of the resistors and capacitors used in the circuit. Changes in these factors can alter the relationship between the input currents and the output voltage.

## 5. How is op amp design used in real-world applications?

Op amp design is used in a wide range of real-world applications, such as audio amplifiers, signal filters, and voltage regulators. They are also commonly used in instrumentation and control systems, as well as in electronic devices like computers and smartphones.

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