California University of Pennsylvania. Department of Applied Engineering & Technology. Electrical / Computer Engineering Technology

Transcription

1 California University of Pennsylvania Department of Applied Engineering & Technology Electrical / Computer Engineering Technology EET 215: Introduction to Instrumentations Lab No.5b Operational Amplifier Names: Signature: Date

2 Operational Amplifiers Objective of the Experiment The main objective of this experiment is to understand the basic functions of an operational amplifier Learning Outcomes Students will demonstrate: - the ability to understand the inverting and the noninverting voltage amplifiers - the ability to use modern tools and demonstrate troubleshooting skills CAUTION: It is imperative that students exercise care when handling the ELVIS unit. Make sure all connections are correctly made. When in doubt, check with your instructor to verify proper circuit connections. Introduction The LM741 is a general purpose operational amplifier. Figure -1 shows the pin-out of the DIP used in lab. Figure -1: LM 741C Refer to class notes as a reference as you do this lab. Components Needed: LM741C op-amp 1KΩ, 2.2 KΩ, 10KΩ, 22KΩ 10KΩ OR 5KΩ potentiometer

3 Vout and Vin, Volts Experiment For all circuits, the +/- V supply = +/- 15Volts. A- Inverting amplifier- Basic With the power to the board initially turned OFF, a- In the space provided below, draw a basic inverting amplifier circuit to have a theoretical voltage gain of -10. Use for Ri the value of (1KΩ, OR 2.2 KΩ.) b- Construct the circuit and apply a sine wave input. The sine wave is at 100Hz and 2Vp-p. c- Neatly, sketch the input and output waveforms. (Same as with previous experiments, connect the input and output to the proper input channels on the ELVIS board. Also, make sure the scope is on dc coupling and that the vertical positions are set to zero.) time, sec. d- The input and the output are said to be degrees out of phase. (fill in the blank)

4 e- From the waveforms on the scope, calculate the experimental voltage gain, Vo(p-p)/Vin(p-p) % difference = A v(experimental) A v(theoretical) A v(theoretical) 100 Av (theoretical) Av (Experimental) %difference f- What is the input impedance (Rin) seen by the source? Rin = Ω B- Inverting amplifier- multi-inputs 1- Construct the circuit shown. For the potentiometer, may use a 10KΩ or a 5 KΩ pot. Note, change Vin to 4V(p-p) 2- Calculate the following: (Theoretical) a- The output waveform will swing between Volts and Volts (fill in the blank) b- The reference level of the output waveform is expected to be: (dc volts) 3- Monitor the input and output waveforms on the scope and sketch the results below.

5 Vout and Vin, Volts time, sec. 4- Compare your results on the scope with the calculated values in step 2. Do the both agree (within 5%)? If yes, continue, otherwise fix the problem. Instructor Sign-off: Calculate: For the same above circuit (Part B), what is the maximum peak input voltage before Vout just saturates? Assume the dc input is still at 1.5V (unchanged) Vin(pk) = Volts 6- Verify the theoretical result in 5 by slowly increasing the amplitude of the input signal until Vout just saturates (about to saturate). What is the corresponding Vin(pk)? Vin(pk ) = Volts 7- If there is more than 5% difference between the results of steps 5 and 6, explain the cause. C- Noninverting amplifier Basic (This part and the challenge [arts are to be done as Homework using Multisim] 1- In the space provided below, draw a basic noninverting amplifier circuit to have a theoretical voltage gain of 11. Use for Ri the value of (1KΩ, OR 2.2 KΩ.)

6 Vout and Vin, Volts 2- Construct the circuit and apply a sine wave input. The sine wave is at 100Hz and 0.5V(pk). 3- Sketch the input and output waveforms time, sec. 4- From the waveforms on the scope, calculate the experimental voltage gain, Vo(p-p)/Vin(p-p) % difference = A v(experimental) A v(theoretical) A v(theoretical) 100 Av (theoretical) Av (Experimental) %difference 5- What is the input impedance, Rin, as seen by the sinusoidal source in part C? Rin = Ω (From the datasheet of the previous experiment) D- Noninverting amplifier Multi-inputs Construct the circuit shown and: a- Theoretically, determine Vout. Vout = Volts (Show work below)

7 b- Measure Vout. Vout = Volts. If the answers in a and b are more than 5% apart, fix the problem. Instructor sign-off: Challenges 1- Neatly draw the circuit for an inverting adder so that Vo = -5(V1 + V2 +V3) where V1, V2, and V3 are arbitrary inputs. 2- Design and draw a circuit to yield the output shown for the given input. Clearly label components and voltages. [ Do not need to construct the circuit.]

8 Vout and Vin, Volts Vout Vin time, sec. Instructor approval of experiment completion: