EXPERIMENT 1: Operational Amplifiers
Due TUESDAY OCT 12, in class

AD741 datasheet

I. DESCRIPTION AND OBJECTIVES

This laboratory presents a basic practical summary of operational amplifiers (op-amps) and will provide the opportunity to become familiar with their behavior from an ideal and non-ideal perspective.


II. GENERAL DISCUSSION

An op-amp is a three-port device having two inputs and one output. It was invented to simplify the design of inverting and non-inverting DC amplifiers by the simple control of external negative feedback. This deceptively simple building block is to analog electronics what nand or nor gates are to digital electronic circuits: it reduces analog circuit design to a simple problem of determining suitable external feedback and interconnecting networks without the complication of having to know what's going on inside the op-amp itself. Treating the op-amp as ideal is often all that is necessary to use it in practice, provided we skillfully appreciate the limitations imposed by basic device parameters that would typically include: non-infinite open-loop gain, frequency response expressed by slew rate, single-pole roll-off frequency and its related gain-bandwidth product GBP, non-infinite input port resistances and non-zero output resistance; power-supply limiting or railing due to finite power supply voltages. Although the op-amp is employed in a truly impressive array of many different circuits, all are based in part on one or both of the following two fundamental circuit configurations, the inverting and non-inverting DC amplifiers. You will gain an appreciation of the power of the op-amp as a basic building block along with some of its inherent limitations by investigation of these two basic circuits.


III. NON-INVERTING CONFIGURATION

Construct the circuit shown in Fig. 1. using an AD741 op-amp. R2 should be 10k. Determine the following for R1 = 1k, and R1 = 10k:

Observe power-supply limiting and log what these voltage rails are. Measure and accurately plot the amplitude and phase response vs. frequency. Frequency should be measured with a counter, amplitude in RMS from a DVM. Measure the slew rate.

Figure 1. Basic non-inverting op-amp configuration. Note: Re-draw this schematic in your engineering notes and make any experimental scribbles or annotations there.

From your data, construct a simple Bode Plot showing both plots for the two different circuit gains. Discuss the meaning of the gain-bandwidth product relationship and verify it from your data. Discuss your results for slew-rate. Numeric data should be discussed with realistic precision using only as many significant figures as your data warrants.

Recommended Procedure:

IV. INVERTING CONFIGURATION

Modify your circuit to realize an inverting amplifier and repeat the measurements taken earlier for the non-inverting configuration . Discuss all differences you observe between the two configurations.


QUESTIONS

You should address these questions in your lab report.

LAB REPORT

The lab report should be proof-read and well written. Check out format.html if you are unsure what is expected. Your lab report should include (at least):