Lab: Operational Amplifiers

Transcription

1 Page 1 of 6 Laboratory Goals Familiarize students with Integrated Circuit (IC) construction on a breadboard Introduce the LM 741 Op-amp and its applications Design and construct an inverting amplifier using the op-amp Measure and record input and output waveforms Compare measured and theoretical values Pre-lab reading LM741 datasheet on the website ( ) Equipment needed Lab notebook, pen Agilent E3631A Triple DC Power Supply Digital Oscilloscope 2 oscilloscope probes (attached to the oscilloscope) Agilent 33220A Function Generator/Arbitrary Waveform Generator 1 test lead, BNC/EZ Hook 2 test leads, red, banana/ez Hook 1 test lead, black, banana/ez Hook Parts needed Circuit breadboard Lab parts kit IC, Operational Amplifier, LM 741 or equivalent Resistors (2), 1k Ohm, ¼ Watt Resistor, ¼ Watt (to be determined by the circuit gain) Jumper wires Lab safety concerns Make sure all circuit connections are correct, and no shorted wires exist. Adjust the power supply to the proper voltages before connecting it to the circuit Adjust signal generator to the proper level before connecting it to the circuit

2 Page 2 of 6 1. Set up & Pre-Lab Amplifier Design Refer to the LM 741 datasheet on the ECE website for the 8-pin diagram before wiring the circuit. Check each of the pins you will use labeled on the schematic below against the function and pin number on the schematic to ensure they are correct. Design the inverting amplifier (shown below in Figure 1) using -2 times the last digit of your or your partner s UNM ID number (select the non-zero number) as the gain (e.g., if your last digit is 1, design the circuit to have a gain of -2) Figure 1: Inverting Operational Amplifier Circuit using LM741 8-pin DIP Measure the actual value you 1 kohms resistor and determine the value of R2, the feedback resistor using the formula: Gain = - (Rf/Ri) where Rf is the feedback resistor (R2) and Ri is the input resistor (R1). Include these calculations in the report.

3 Page 3 of 6 Create a table in your lab notebook similar to the one below for the amplifier (an example column is shown). The test points are 100Hz, 300Hz, 1kHz, 3kHz, 10kHz, 30kHz, 100kHz, 300kHz, 1MHz input frequencies. (Note this is not the Results Table but it should be included with the Results Table in the report s Verification Results section.) Frequency Vin Amplitude (Vpp) Amplitude(Vpp) Vout Phase Shift degrees Gain (Vout/Vin) 100 Hz 300 Hz 1 khz 3 khz 10 khz 30 khz 100 khz 300 khz 1 MHz Table 1: Table for recording input and output characteristics of Inverting Amplifier 2. Circuit Construction and Signal Measurement Build the circuit as shown above in figure 1. (For resistor R2, use the closest available resistor value (found in the cabinet) to your calculated R2) Using the measured value of this selected resistor R2, calculate the expected gain of the actual circuit. Included these calculation in the report. This is the expected value that will be used in the report s results table. Setup for the Agilent power supply: o Press the Output On/Off button to enable the power supply output o Press the +25V button to select the +/- 25V power supply o Adjust the power supply output to +15VDC o Press and hold the Track button (this allows the negative supply to automatically track the positive supply voltage setting) o Press the Output On/Off button to disable the power supply output Connect a red banana/ez Hook test lead between the + output (+/-25V terminals) and the circuit +15 V connection of the Amplifier Circuit in Figure 1. Connect a another red banana/ez Hook test lead between the - output (+/-25V terminals) and the circuit -15 V connection of the Amplifier Circuit in Figure 1. Connect a black banana/ez Hook test lead between the COM power supply ground and the circuit ground connection of the Amplifier Circuit in Figure 1.

4 Page 4 of 6 Double check the connections and the Op Amp pin numbers to ensure the proper configuration. Setup the Agilent oscilloscope: o Press the ON button o Briefly test the CH1 and CH2 oscilloscope probes using the Probe Comp test point (always make sure the probes are working correctly before using them!) o Connect Channel 1 probe to the Amplifier Circuit input (See Figure 1) o Connect Channel 2 probe to the Amplifier Circuit Output (See Figure 1) Setup the Agilent function generator: o Set the instrument for high impedance (HIGHZ) output o Sine waveform o Amplitude = 1Vpp o Frequency = 100Hz o Offset = 0Vpp o Output off Connect the BNC/EZ Hook test lead to the function generator OUTPUT Connect the red and black ends of the EZ Hook test lead to the circuit input and ground connections of the Amplifier Circuit of figure 1 respectively Connect the CH1 oscilloscope probe and ground clip to the circuit input and ground connections respectively Connect the CH2 oscilloscope probe and ground clip to the circuit output and ground connections respectively Double check all connect to ensure proper configuration. Turn on the OUTPUT of the Power Supply and the OUTPUT of the function generator Ensure the Op Amp is not overheating. Be careful not to get burned! Using the Oscilloscope Controls, adjust the display so it presents the input and output signals such that the amplitudes and phase angles can be measured. Record in your table the circuit input voltage, output voltage, and phase shift (in degrees). Remember, for phase shift measurements: o Measure with the X-t mode td/t1 method from last lab o Include each td and t1 and the calculations of the phase shifts in the report.

5 Page 5 of 6 Repeat the voltage and phase shift measurements for each of the required test frequencies Calculate the gain for each frequency, and record it on your table After all the measurements have been recorded and checked by a T/A, turn the power supply output off (OUTPUT) and turn the function generator output off (OUTPUT). Unclip all of the test leads from the circuit, and turn off the equipment Return the Op Amp to the T/A Return all components and test leads to their proper places Before leaving the lab, 1. ensure that your measured values are reasonably close to the calculated expected values, 2. take a few minutes to make sure all equipment and test leads are returned to your cabinet, and 3. that you have cleaned up your work space. 3 Analysis Ensure that all measurements have been properly recorded and will be available for uses after the next Lab has been completed. This lab information will be combined with next week s lab information to produce a single Operational Amplifier lab report. The report for this lab is to be written after completing both the Operational Amplifier labs.

6 Page 6 of 6 5. Revision History Version: Description: Date: Author: Initial release Nov. 01, 2017 D. R. Modisette Correct Schematic Fig 1, Nov. 08, 2017 D. R. Modisette Spelling, & Grammar