OP Amps II

In this lab we further explore operational amplifiers by observing the effects of changing the input and feedback resistors. We began the lab with the first set of values being:

Resistor	Nominal Value	Measured Value
R1	10K Ω	9.79k Ω
R2	100k Ω	95.2k Ω

The current leaving the op-amp is 0.1 mA

After setting up our circuit we recorded the values  for various V in values.

V in Desired	V in actual	V out measured	V RF measured	I op Calculated
0.25 V	0.251 V	2.49 V	2.50 V	0.0263 mA
0.5 V	0.433 V	4.25 V	4.26 V	0.0447 mA
1.0 V	1.192 V	10.76 V	10.79 V	0.113 mA

ICC = 1.01 mA   IEE = -0.91 mA

We see that KCL for the op amp is true
Irail = IEE + ICC = 0.1 mA
Power calculated
PIcc = 12V *1.01 mA = 12.12 mW
PIEE = 12V * (-.91 mA) = -10.92 mW

We then add a 1k resistor to our circuit and remeasure the values when V in = 1.0 V

V in Desired	V out measured	V RF measured	I op calculated	I cc measured	I EE measured
0.93 V	9.39 V	8.99 V	0.094 mA	0.93 mA	-1.04 mA

KCL still holds  Icc + IEE = 0.11 mA
Power calculated

PIcc = 12V *0.93 mA = 11.16 mW
PIEE = 12V * (-1.04 mA) = -12.48 mW


We then reproduce the lab by replacing Rf = 50k ohms which we set with a resistor box.

V in Desired	V out measured	V Rf measured	I op calculated	I cc measured	I EE measured
1.08 V	5.44 V	5.47 V	0.109 mA	0.9 mA	-1.01 mA

The measurements still behave as expected. KCL holds.