3/26/2015

Today, we focused primarily on operational amplifiers and their use in electrical circuits.

Original

After analyzing circuit with an op-amp we were given the circuit above and asked to find the closed circuit gain and i_0.

Replacement

When given circuit that includes an op-amp we are able to replace the op-amp symbol with the element shown above.

Example Problem

 Circuit analyzed above.

Built Circuit

This lab required the use of an op-amp in order to find saturation. Above is the built circuit.

Results

In order to find the saturation caused by the op-amp, we supplied various voltages ranging from -3-3V. 

Graph of V(in) VS. V(in)

We found that that the voltage began saturating when voltages above 2V or -2V were supplied. Ideally the voltage coming out of the op-amp should be 5V but because the op-amp was inexpensive meant that not so good materials were used which would lead to some voltage loss.

Summary:

Today, we focused primarily on the use of operational amplifiers and the analysis of the instrument in a circuit. Operational amplifiers have a set value for open-loop gain, input resistance and output resistance. However, we can treat operational amplifiers like ideal op-amps and let their open-loop gain and input resistance go to infinity and their output resistance go to zero. We can treat modern op-amps like ideal op-amps because they have large gain and input resistance values. Two very important characteristics of an ideal op-amp is that both input currents into the op-amp are zero (because infinite input resistance) and the voltage across the input terminals are small (V_d refer to 2nd picture).