D11 - Op Amps 2

We started the day with talking about unity gain buffers were Vin = Vout. And then moved onto an Inverting Amplifier with a square wave being input to it. We drew our predicted sketch of Vout.

White Board work of showing the amplification of the Op amp signal, note how the second graph raises above zero.

White Board work on the Inverting Op amp with a sqaure wave. Vout = -Rf/Rin*Vin. If -Vcc is tied to ground no voltage output below zero will be shown.

We then move onto an example of an ideal Inverting Op Amp. Vs = 0

White Board work, we used Node Voltage on the negative node of the Op amp.

More White Board work, we found Vo in terms of Va and plugged it into the other Node b and got Vout = -3.27 V.

We then move onto the Non-Inverting Op amp. We discussed its properties and came out with the formula Vout = (1+Rf/R1)*Vin.

White Board work of getting the formula for a Non-Inverting Op Amp.

We further talked about a summing amplifier and showed that -Vout = Rf/R1*V1 + all the to other input resistance under Rf * there respected V's.

White Board work of coming to the conclusion of -Vout = V1 + V2 + V3 if all the resistors are the same in a summing amplifier.

We then move onto the lab:
Summing Amplifier.
PreLab:
Va and Vb should see input of at least R1 and R2 being 1 k ohms.

Picture of our summing amplifier circuit.

Pre lab White Board work. R1 = 5.8 k, R2 = 5.8k k, and R3 = 4.8 k and Vb = 1 V.

White board Data, ranging Va from -4 V to 5 V. Vout responded with 2.44 V to -3.45 V, respectively.

We then move onto a Difference Amplifier. The difference amplifier amplifies the difference between two inputs and rejects any signal common to the two inputs. We were asked to sketch some graphs.

White board work of the sketch required of class, not sure of what? Difference amplifiers?

Anyways, we then asked to an problem with designing a difference amplifier with gain of 2 and common mode of input resistance of 10 k ohms at each input.

White Board work, circuit schematic of difference amplifier and used Vo = R2/R1(V2-V1). We found R needed to be 20 k ohms.

We then move onto more examples of difference amplifiers.

White board work of a square wave being fed into the difference amplifier.

More White Board work, right side of the same problem, we used Node voltage Va and Vb found Va = Vb and then got Vout = 1/3 Vin.

In summary we talked about many types of Op Amps starting with unity buffers which just output Vin,  Inverting Op amps which invert and amplify the input, and Non-Inverting Op Amps, which amplify the input and lastly Difference Op Amp which amplify the difference of the inputs. We did a lab for the Summing amplifiers which take each input resistance under Rf and times it with their respected V and sums them together. And finished the class with examples of difference amplifiers which was suppose to be another lab but did not do, however our white board work showed the important relationship of r1/r2 = r3/r4 is in the difference amplifier.