lab5_opamps

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EECS 215 Laboratory 5 – Op Amps L ABORATORY 5 – O P -A MPS Name: Lab Section #: Submission instructions: Use this document as your lab report template. Fill in the tables below as instructed, save as PDF, and submit your lab report on Gradescope one week after your 2 nd scheduled lab session (this is a 2-week lab). Laboratory 5 – Op-Amps 1 Part List 1 Introduction 2 Laboratory: Part One - Single Stage Inverting Amp 2 Laboratory: Part Two - Inverting Summing Amp 7 Laboratory: Part Three - Non-Inverting Amp 10 Laboratory: Part Four- Two Stage Non-Inverting Amp 12 1. P ARTS L IST 1. LM224N Quad opamp 2. 2 electrolytic capacitors 1µ𝐹 3. 2 resistors 4. 7?Ω 4. 2 resistors 47?Ω 5. 1 resistor 470?Ω 6. 1 resistor 10?Ω 7. wire 2. I NTRODUCTION In this lab you will learn how to set up your own inverting, non-inverting, and two stage non-inverting amplifiers using one LM224N chip ( data sheet ) from your kit. Using the waveform generator, power supply, and oscilloscope from your AD2, you will be able to power the op amp 1

EECS 215 Laboratory 5 – Op Amps and visualize the gain of the amplifiers being applied to the input signal. This lab is designed to be completed in a two week period. Figure 1: LM224N Quad Opamp chip diagram. “GND” pin is the negative supply terminal. For this lab it is important to know how to calculate the gain of the different op amps. There are two equations that you will need to use in order to calculate the ideal gain of the amplifier. ● Inverting Amps: Gain = −𝑅2 𝑅1 ● Non-Inverting Amps: Gain = 1 + 𝑅2 𝑅1 When amplifiers have a negative gain, this results in having a phase shift of 180 degrees. 3. L ABORATORY : P ART O NE - S INGLE S TAGE I NVERTING A MP In this part of the lab, you will create an amplifier that inverts the input signal and increases the amplitude by a certain gain. In this part, you will calculate the ideal gain for each op amp, and compare the value to the gain measured from your AD2 2

EECS 215 Laboratory 5 – Op Amps Figure 2: Inverting Amp Schematic 1. Derive an expression for Vout as a function of Vin, where Vin is the node connected to the Waveform Generator. Show your equations below, either typed or a picture of your handwritten work. Derivation of Vout {insert here} 2. Set up the circuit and hook up the AD2 as shown in Figure 2 above. Be sure to use the LM224N chip for this lab, and refer to the diagram in Figure 1 for specific pin numbers. Include a picture of your circuit below. a. Note the position of the dot is next to pin #1 when mapping pins. b. Make sure that the V+ lead, solid red, from the AD2 is attached to pin #4. c. Make sure that the V- lead , solid white, from the AD2 is attached to pin #11. Picture of Circuit 3

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EECS 215 Laboratory 5 – Op Amps {insert here} 3. We want to compare our input from the Waveform Generator to the output of the amplifier at V Out . Place the Channel 1 positive lead to the same node as the waveform generator, and place the Channel 2 positive lead to V Out . a. Both Channel 1 and 2 negative leads are connected to ground. 4. Open the WaveForms program and open the Waveform Generator, Oscilloscope, and Power Supplies. 5. Set your positive (V+) and negative (V-) supply to voltage of +5 and -5, respectively. 6. We want to set our input signal to be a small amplitude to keep the amplifier in the linear region where our equations hold true, opposed to the saturation region where our equations do not. Set your Waveform Generator to the following parameters: a. Frequency: 1 kHz b. Amplitude: 10 mV c. Leave all other parameters unchanged The wavegenerator might have some dc offset (~ 5 mV) at the input voltage. Also, the ± opamp offset voltage may contribute to DC offsets at the output. For all your measurements in this lab, you should estimate the DC offset voltages for the input and output, and find the gain from the amplitudes of the AC part of the waveform. This can be done several ways. A very simple approach is to use the peak to valley voltages to get twice the amplitude and to 𝑉𝑝𝑝 = 𝑉𝑝𝑒𝑎? − 𝑉𝑣𝑎??𝑒𝑦 ( ) 1 2 𝑉𝑝𝑒𝑎? + 𝑉𝑣𝑎??𝑒𝑦 ( ) estimate the DC offset. Use the Vpp and Vmiddle settings on the AD2 scope to get these values. A more sophisticated method is to fit waveforms to the input and output data. 4

EECS 215 Laboratory 5 – Op Amps Note: This is for demonstration purpose only for measuring peak-to-peak values. In this figure, Ch1 is the output, and Ch2 is the input. 7. Using a cursor on the oscilloscope, find the gain of the amplifier. How does this gain value compare to ideal op-amp theory? If your values are off by more than 10%, determine where your mistakes are, fix them, and repeat this step. V pp,Out (measured): V Out,offset (measured): V pp,in (measured): V in,offset (measured): Gain (measured): Gain (ideal): 8. Include a screenshot of your Waveform graph with cursors. This can be done by selecting Export → Image. Save the data as “Data1.csv” using Export → Data as shown below (data must be taken from your circuit with your AD2). Upload csv files to CANVAS with your lab submission. 5

EECS 215 Laboratory 5 – Op Amps Screenshot of Waveforms {insert here} 9. Note: You can see that the input is high when the output V Out is low and vice-versa. This is termed “out of phase” and is a consequence of using a negative gain amplifier, as you can determine from the equations given. a. Ex. For an inverting amplifier with a negative gain, the input is related to the output by: Out = Gain * In If the input was a sinusoid with amplitude A and angle Θ, you would expect a sinusoid as the output with an adjusted magnitude and a phase shifted 180 degrees from the input. vout = A*Gain*sin(Θ) Using the trigonometric identity -sin(x) =sin(x+180) and remembering the gain is negative we can rewrite the output. 6

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EECS 215 Laboratory 5 – Op Amps A*Gain*sin(Θ) = A*|Gain|*sin(Θ+180) Optional For practice, you can use the network analyzer on WaveForms to measure the frequency response of the circuit using “Logarithmic” scale setting from 100 Hz to 10 MHz. This generates a Bode Plot, which will be discussed more in class later in the semester. Noting where the magnitude falls off by - 3dB is how we define the corner frequency. What is the approximate corner frequency for this circuit? 7

EECS 215 Laboratory 5 – Op Amps 4. L ABORATORY : P ART T WO - I NVERTING S UMMING A MP In this section of the lab, you will be repeating Part One from above, but adding in another waveform generator to create a summing amp. Figure 3: Inverting Summing Amp Schematic 1. Derive an expression for Vout as a function of Vin1 and Vin2, where Vin1 and Vin2 are the nodes connected to the two Waveform Generator signals. Show your equations below, either typed or a picture of your handwritten work. Derivation of Vout {insert here} 2. Set up the circuit and hook up AD2 as shown in Figure 3 above. Be sure to use the LM224N chip for this lab, and refer to the diagram in Figure 1 for specific pin numbers. 8

EECS 215 Laboratory 5 – Op Amps 3. Use scope channel 2 to measure vout. You will need to move the scope channel-one probe for separate measurements of W1 and W2. 4. In order to change the parameters for waveform generator 2, you must change the channel of the waveform generator to channel 2. This will be the second signal that is being summed with the first. 5. Repeat steps 3-6 from Part One. Picture of Circuit {insert here} 6. Using the same numbers for Channel 1 of the waveform generator as in Part One, set your channel 2 parameters to the following: ● Frequency: 3 kHz ● Amplitude: 10 mV *** please make sure the output of the two channels are synchronized. Save the data as “Data2.csv” (data must be taken from your circuit with your AD2). Upload csv files to CANVAS with your lab submission. Screenshot of Waveforms {insert here} 7. Using a cursor on the oscilloscope, find the gain of the amplifier from each input to the output. How does this gain value compare to ideal op-amp theory? ( For this step, you need to turn off one of the generators to calculate the gains individually) V pp,Out1 (measured): V Out,offset1 (measured): V pp,in1 (measured): V in,offset1 (measured): Gain1 (measured): Gain1 (ideal): V pp,Out2 (measured): 9

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EECS 215 Laboratory 5 – Op Amps V Out,offset2 (measured): V p,pin2 (measured): V in,offset2 (measured): Gain2 (measured): Gain2 (ideal): 8. Include a screenshot of your Waveform graph with cursors .Save the data as “Data3.csv” (data must be taken from your circuit with your AD2). Upload csv files to CANVAS with your lab submission. Screenshot of Waveforms (2 screenshots) {insert here} 10

EECS 215 Laboratory 5 – Op Amps 5. L ABORATORY : P ART T HREE - N ON -I NVERTING A MP Figure 4: Non-Inverting Amp Schematic After setting up your circuit shown in Figure 4, you will be repeating Part One from above, but changing your op amp to be a non-inverting amp. 1. Derive an expression for Vout as a function of Vin, where Vin is the nodes connected to the Waveform Generator signal. Show your equations below, either typed or a picture of your handwritten work. Derivation of Vout {insert here} 11

EECS 215 Laboratory 5 – Op Amps 2. Set up the circuit and hook up AD2 as shown in Figure 4 above. Be sure to use the LM224N chip for this lab, and refer to the diagram in Figure 1 for specific pin numbers. ● Make sure that your waveform generator is connected to the positive pin of your op amp. 3. Repeat steps 3-6 from Part One. Picture of Circuit {insert here} 4. Using a cursor on the oscilloscope, find the gain of the amplifier. How does this gain value compare to ideal op-amp theory? Include a screenshot of Waveforms. Save the data as “Data4.csv” (data must be taken from your circuit with your AD2). Upload csv files to CANVAS with your lab submission. V pp,Out (measured): V Out,offset (measured): V p,pin (measured): V in,offset (measured): Gain (measured): Gain (ideal): Screenshot of Waveforms {insert here} 5. Note: You can see that the input and V Out are out in phase here since it is a positive gain amplifier, as you can determine from the equations given. 6. Carefully increase the amplitude of your input signal from the waveform generator until you first see clipping on V Out . Note the input amplitude where this occurs. Does the amplitude make sense? Take a screenshot of the Waveforms while the output is clipping. 12

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EECS 215 Laboratory 5 – Op Amps Save the data as “Data5.csv” (data must be taken from your circuit with your AD2). Upload csv files to CANVAS with your lab submission. Screenshot of Waveforms {insert here} 6. L ABORATORY : P ART F OUR - T WO S TAGE N ON -I NVERTING A MP Figure 5: Two Stage Non-Inverting Amp Schematic For this part of the lab, you will be making a two-stage non-inverting amplifier using two op-amps. We will still be using the LM224N chip to do this, by utilizing two of the four op-amps available. It is important to make sure that your output of the first op-amp is connected to the positive input pin for the other op-amp. Note: Feedback resistors are changed to 47kOhm 1. Derive an expression for Vout as a function of Vin, where Vin is the nodes connected to the Waveform Generator signal. Show your equations below, either typed or a picture of your handwritten work. 13

EECS 215 Laboratory 5 – Op Amps Derivation of Vout {insert here} 2. Set up the circuit and hook up AD2 as shown in Figure 5 above. Be sure to use the LM224N chip for this lab, and refer to the diagram in Figure 1 for specific pin numbers. 3. Repeat steps 3-6 from Part One. Picture of Circuit {insert here} 4. Using a cursor on the oscilloscope, find the gain of the amplifier. How does this gain value compare to ideal op-amp theory? How does this gain compare to the gain of a single stage amplifier? Include a screenshot of Waveforms. Save the data as “Data6.csv” (data must be taken from your circuit with your AD2). Upload csv files to CANVAS with your lab submission. V pp,Out (measured): V Out,offset (measured): V p,pin (measured): V in,offset (measured): Gain (measured): Gain (ideal): Screenshot of Waveforms {insert here} 5. Note: You can see that the input and V Out are out in phase here since it is a positive gain amplifier, as you can determine from the equations given. Optional 14

EECS 215 Laboratory 5 – Op Amps Use the Network Analyzer on Waveforms and measure the frequency response of this circuit from 100 Hz to 10 MHz. This will generate a Bode plot. Details of this will be discussed later in the class. Noting where the magnitude falls off by - 3dB is how we define the corner frequency. What is the approximate corner frequency for this circuit? How does it compare to the single stage case? Though it will take us a little while to explain gain - bandwidth product issues, this experiment illustrates that we can trade - off the gain of a stage for increased frequency response. 15

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