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Spring 11 Lab 3 - Op Amps Lab 3-2
2. Set the Agilent 34405A DMM to read DC voltages. Use the 4-1/2
digit display(rather than the default 5-1/2 digit display) to
reduce the effects of noise in thecircuit.
3. Turn the 20V Voltage Adjust knob on the Agilent E3630A power
supply to createthe desired input voltages, E I, shown below in
Table 1. It is not necessary to getexactly the nominal voltage
noted in the table, within 0.02 volt is close enough.
4. Use the DMM to measure voltage E I at the input to the
resistor R 1 and voltage E O atthe output of the inverting op amp
circuit as shown in Figure 1. Record the inputvoltages E I and
output voltages EO exactly as read from the DMM.
Do NOT record or use the voltage displayed on the Agilent E3630A
power supply.
Table 1
Nominal Input Voltages E 1 for Lab Exercise 3.1
+0.4 V +0.8 V +1.2 V +1.6 V +2.0 V +2.4 V +2.8 V
+3.2 V +3.6 V +4.0 V +4.4 V +4.8 V +5.2 V +5.6 V
-0.4 V -0.8 V -1.2 V -1.6 V -2.0 V -2.4 V -2.8 V
-3.2 V -3.6 V -4.0 V -4.4 V -4.8 V -5.2 V -5.6 V
5. After collecting this data set #1, disconnect the power to
the solderless breadboardand remove the 741 op-amp chip. Do NOT
change any of the wiring or resistors!
6. Insert a different 741 op-amp chip into the circuit do NOT
change any of the wiringor resistors! Reconnect the power to the
solderless breadboard and repeat all of the
measurements from step #3 with a different student taking the
measurements. Thiswill be data set #2.
7. After collecting both sets of data from two different 741
op-amp chips, remove theinput resistor R1 and feedback resistor R2
from the board. Measure and record theirresistances (use the 4
digit display to reduce effects of noise). These resistancevalues
will be used in the formula to compute the theoretical gain for the
op-ampcircuit.
Outside of Lab:
8. Plot measured E O vs. measured E I for data set #1. On the
plot, clearly identify the
linear region of E O vs. E I, i.e., where E O vs. E I is along a
line of constant slope.9. Determine the least-squares best fit
experimental gain for the data in the linear region,
E O = G exp1 E I
Use Excels Trendline function and force the line to go through 0
to determine G exp1(or use the pseudo-inverse method of ME 349). Do
NOT include a constant offsetvoltage.
