EE 101

Lab Exercise 11: The 741 Operational Amplifier

 

(There is no pre-lab for this exercise)

 

 In this lab, you will design and build several operational amplifier circuits on the breadboard.

 

Figure 1: The 741 Op-Amp

 

 Use -Vcc = -15V and +Vcc = +15V for all circuits.

1. Build the circuit shown in Figure 2 (inverting op-amp) on the protoboard. After your wiring has been checked by a lab assistant, apply a 5 volt input voltage, instead of the 1V input. Measure and record Vout. Is this the value you expected to see? How close was your answer to your calculated result (do a percent difference).

 

 

Figure 2: Inverting Configuration

 

 

2. Build the circuit shown in Figure 3 (non-inverting op-amp). Apply a 5 volt input voltage. Measure and record Vout. Is this the value you expected to get? How close is it to your expected value (percent difference)?

 

Figure 3: Non-inverting Configuration

 

3. For the above problems (1 and 2), what is the highest and lowest input voltages you could apply to each circuit before the op-amp would "rail"?

4. Design and build a cascaded op-amp circuit with a total gain of +1/8 (Refer to your class notes for assistance, if necessary). Apply a 5 volt input signal and record Vout. Is Vout one-eighth of Vin? How close is your result to what you ideally would get?

5. Design and build an op-amp circuit with a total gain of 3.25. Apply a 5 volt input signal and record Vout. Record your result for Vout.

6. Design and build an op-amp circuit with a total gain of -3.25. Apply a 5 volt input signal and record Vout. Record your result for Vout.

 

Questions

1. How could you design a circuit to provide a gain of 1/8 to an input signal without using an op-amp?

2. In problems 5 and 6, were your outputs 3.25 (or -3.25) times the magnitude or your inputs? Explain why or why not.

 


June 2000

Copyright 2000, New Mexico Tech