4/6 Summing Amplifier & Difference Amplifier

We learned many other amplifiers today.
We started with the unity gain buffer amplifier.

We did a example to calculate the Vo if Vs = 0 in the circuit above.
By using nodal analysis, we got Vo = -1.6364V.

And then, we talked about Non-inverting Amplifier which is an op amp circuit designed to provide a positive voltage gain.
The relationship between Vin and Vout of non-inverting amplifier is:

Next, we talked about Summing Amplifier.
The relationship between Vin and Vout of summing amplifier is:

indicating that the output voltage is the sum of the inputs. 

Then, we did lab.

Summing Amplifier

The picture above is the basic set up for this lab.

In this lab, the relationship between Vin and Vout is:

The actual resistance of R1=6.71k ohms

R2=6.67k ohms

R3=6.73k ohms

We got the following table and graph.

The data matched the equation.

For Va=3V and 5V, Vout is at saturation.

The picture is the calculated data we expected to get, but the maximum Vout we could get is 5V and -5V, so we can only get the Vout up to -3.44V.

After summing amplifier lab, we talked about Difference Amplifier.

The relationship between Vin and Vout is:

the amplifier must have the property that Vo = 0 when  V1 = V2 . This property exists when

so we can get:

Difference Amplifier

The picture above is the basic set up for this lab.

The relationship between the input and output voltages we determined in the class is the picture below.

The actual resistance of R1=9.94k ohms, R2=19.9k ohms, R3=9.98k ohms, and R4=19.7k ohms.

The table above is when we set Vb=1V, and vary Va.

We got the graph below:

From the data we got, it followed the relationship between the input and output voltages we determined in the class. 

For Va=-4V, -2V, 3V and 5V, Vout is at saturation.

After this lab, we ended up with analyzing a circuit below:

 

This is a non-inverting amplifier circuit.

By using nodal analysis, we can get the relationship between VL and VT.

Summary

We learned about Non-inverting Amplifier, Summing Amplifier, and Difference Amplifier today. By doing the lab, we knew how each amplifier works and what are the differences between different amplifiers. Each amplifier works differently in the circuit, and the relationship between the input and output voltages are different, too. Next class we will learn more amplifiers which are called differentiation and integration amplifiers.