Inverting Voltage Amplifier

In this class meeting, we learned about operational amplifiers...

We did some problems first (1)

We did some problems first(2)

We did additional problems (we got 0 as answer when the correct answer was 9 V, we used 2000 as our open loop voltage gain when it was actually 2*10^5.)

Starting the lab...

The setup(1) We choose 4.7k-ohm and 2.2k-ohm resistors.

The setup(2)

The setup(3)

The setup (4)

We measured actual resistance of resistors and output voltage for each input voltage(we did not measure output voltage for negative voltage(we forgot)), and the V_out should have negative relationship with V_in;
Actual resistance for resistors were 4.67k for 4.7k-ohm resistor and 2.16k for 2.2k-ohm resistor(wrote vertically).

V_in	V_out	Expected V_out
0	0	0
0.5	1.07	1.081018519
0.75	1.61	1.621527778
1	2.15	2.162037037
1.25	2.69	2.702546296
1.5	3.23	3.243055556
1.75	3.46	3.783564815
2	3.45	4.324074074
2.5	3.45	5.405092593
3	3.45	6.486111111

Summary: This lab was easy. We choose 2.2k-ohm and 4.7k-ohm resistor to try to get voltage change to two times as input voltage. The actual resistance of resistor was 2.16k and 4.67k respectively. However we got positive multiplication of V_in, but everybody else in class was talking about they got negative multiplication of V_in. So we must measured V_out with negative terminal of multimeter and connect positive terminal with ground. Also we forgot to measure negative V_in. From the graph and data table, we can clearly see that V_out does not go beyond 3.434V, V_out goes beyond was saturated. However, our positive limit voltage was 5V and negative limit voltage was -5V. Instructor later explained that OP-27 does not bound its V_out to its positive and negative limit voltage, that's why it does not go beyond 3.43V. The V_out smaller than 3.43V was consistent with expected V_out=(V_in *(4.67/2.16)).

V_in

V_out

Expected V_out

0

0

0

0.5

1.07

1.081018519

0.75

1.61

1.621527778

1

2.15

2.162037037

1.25

2.69

2.702546296

1.5

3.23

3.243055556

1.75

3.46

3.783564815

2

3.45

4.324074074

2.5

3.45

5.405092593

3

3.45

6.486111111