Build and Analyze a MOSFET Audio Amplifier Circuit

School

University of Michigan**We aren't endorsed by this school

Course

EECS 215

Subject

Electrical Engineering

Date

Dec 10, 2024

Pages

Uploaded by BrigadierWillpowerMeerkat36

EECS 215Laboratory 2 –SpeakerLABORATORY2 – MOSFET AUDIOAMPLIFIER/SPEAKERLABORATORY2 – MOSFET AUDIOAMPLIFIER/SPEAKER11.INTRODUCTION12.LABORATORY: STEPONE13.LABORATORY: STEPTWO34.LABORATORY: STEPTHREE55.LABORATORY: STEPFOUR66.LABORATORY: STEPFIVE7This lab is intended to be completed in 1 lab session. Get your results signed off by yourlab instructor at the end of your lab session. Submit the report on Gradescope. Use thisdocument as a template.1.INTRODUCTIONIn this lab you will drive a speaker to the waveform generator, and learn how to build andanalyze a circuit containing a MOSFET, potentiometer, and capacitor. You will also learn how touse the AD2 “Supplies” and “Wavegen” features while working with audio frequencies andamplitudes from the waveform generator. This lab is designed to be completed in a one weekperiod.2.LABORATORY: STEPONEFirst, you will have to obtain the following components to begin building the circuit as seen inFigure 1:●One Speaker●One 470 Ω Resistor●One ZVN3310 N-Channel MOSFET (Datasheet)(https://www.diodes.com/assets/Datasheets/ZVN3310A.pdf)●One 10 kΩ Potentiometer1 of 11

EECS 215Laboratory 2 –Speaker●One 0.1 µF capacitorFigure 1: Step One Speaker SchematicBefore building the circuit, measure the value of the 470 Ω resistor and Speaker. In order tomeasure the 470 Ω resistor, set your DMM to the 2000 Ω setting; while the speaker is a muchsmaller resistance (<10 Ω) so set the DMM to the 200 Ω setting. Record the resistancesmeasured below:ComponentMeasured ResistanceRSpeaker461 ΩR470Ω7.757 ΩFinally, assemble the circuit shown in Figure 2 and connect the AD2 leads to the circuit asshown. The V+ lead from the AD2 is the positive power supply of 5V which we will controlusing the “Supplies” WaveForms program. The solid orange lead is the positive channel 1 scope,2 of 11

EECS 215Laboratory 2 –Speakerwhile the orange and white striped lead is the negative channel 1 scope. The black lead isconnected to ground (there are multiples of these from the AD2, any will work).Figure 2: Step One Speaker Schematic connected to AD23.LABORATORY: STEPTWONow you will conduct a DC sweep using the potentiometer whilemeasuring the voltage at the “Gate” of the MOSFET. From the figure tothe right, we can measure VGateby using the AD2 channel 2 of the scope.1.Attach the solid blue lead to the “Gate” of the MOSFETa.The solid blue lead is the positive channel 2 scope.2.Attach the blue and white striped lead to GND.a.The blue and white striped lead is the negative channel 2scope.3.In order to power the speaker, open the “Supplies” tab in WaveForms and set the“Positive Supply (V+)” to have a voltage of 5 V, and push the button to turn it on.4.Open the Scope in order to read the voltages for the two scope leads.3 of 11

EECS 215Laboratory 2 –Speaker5.Tune your potentiometer until you readVGate= 0Vand record the voltage at VOut:VGate0VVOut5V6.Next, tune your potentiometer until you readVGate= 5Vand record the voltage at VOut:VGate5VVOut65m V7.To conduct the DC sweep, turn the screw on your potentiometer while watching thevoltage at VGate. Tune it to make 500 mV steps from 0 to 5 V at VGateand record thevalues of VGatevoltage and VOutvoltage at each step.VGate(V)VOut(V)VGate(V)VOut(V)0 VValue V3V0.100V0.5V5V3.5V0.080V1V5V4V0.070V1.5V5V4.5V0.065V2V3.9V5V0.060V2.5V0.150V8.For the remainder of the lab, tune your potentiometer while watching the voltage at VOutand adjust it until VOutmeasures 2.5 Volts; at this point, VGateshould be somewhat close toyour threshold voltage. Measure the corresponding voltage at VGate.VGate2.2VVOut2.5 V4 of 11

EECS 215Laboratory 2 –Speaker9.Optional (not required): Compare the V_Gate value you get from step 8 with the givenLTspice simulation (‘MOSFET_CIRCUIT_2.asc’) of DC operating point. Do theymatch?4.LABORATORY: STEPTHREEFigure 3: Speaker Schematic with waveform generator connected to AD2In order to play sounds from our speaker, we must first hook up our waveform generator to thecircuit.1.Add your 0.1 µF capacitor to the circuit, as seen in Figure 3. The capacitor is used as ahigh-pass filter, to block the DC signal from the AD2 but allow audio frequency signalsto pass to the gate of the MOSFET.a.When looking for your capacitor, it should read “BC 104”.2.Attach the solid yellow lead to the circuit, as seen in Figure 3.a.The solid yellow lead is the first waveform generator lead.3.We need to next “bias” the MOSFET (you’ll learn more about this in EECS 311).a.Tune your potentiometer to 2.5 V at output.4.Open the waveform generator (your scope and power supply should still be on andrunning).5 of 11

EECS 215Laboratory 2 –Speaker5.Set your frequency to 1 kHz, and leave the other parameters as is.6.Slowly increase your amplitude until you see a nice sine wave at VOut. The sine waveshould look similar to Figure 5, with a voltage swing of about 3V. If the amplitude ofinput from the signal generator is too high, you will get a large voltage swing but thesignal will be obviously distorted (not a pure sine wave). You may need to decrease thewaveform generator amplitude below 1V to get a 3V swing and sinusoidal behavior.Figure 5: Sine wave measured from Vout7.Add a picture of your Breadboard, and your Scope waveform with 1kHz signal in thetable below.Picture of Your BreadboardScreenshot of Scope Waveform6 of 11

EECS 215Laboratory 2 –Speaker8.Are you able to hear any sound from the speaker?YES9.Optional (not required): Compare the Vout waveform you get from step 7 with the givenLTspice simulation (‘MOSFET_CIRCUIT_3.asc’) Vout waveform. Do they match?5.LABORATORY: STEPFOURAt the start of this section, make sure your Channel 1 of the oscilloscope is measuring VOut, whileChannel 2 is measuring VGate. You are going to use WaveForms’ “Scope” to plot VGatevs. VOutusing the XY mode.1.Confirm that your power supply, waveform generator, and oscilloscope are all running inthe WaveForms program. Your circuit should be hooked up to your AD2 as seen inFigure 3.2.At the top of the oscilloscope, click the “+XY” tab.3.Set the X axis to be VGate.4.Set the Y axis to be VOut.5.Slowly increase the Amplitude until you have plotted the transfer function in the XYwindow.6.Show a screenshot of your plot in XY mode.7 of 11

EECS 215Laboratory 2 –SpeakerXY Mode Plot7.Save your Waveforms data to a csv file:a.Click Export on the top left and select the “Data” tab at the topb.Change the “Source” to XY1c.Save the data as a csv, something like 'lab 4 XY data.csv'8.Go to Canvas and download our template matlab plotting file (‘lab 4 plotting.m’)9.Open ‘lab 4 plotting.m’ in Matlaba.Make sure your saved XY data file is in the same directory as the matlab fileb.Enter your points fromLaboratory: Step Twoabove as your measured data.c.Run the code to create a matlab plot of VGatevs. VOut8 of 11

EECS 215Laboratory 2 –Speaker10. Insert your Matlab plot below. If the measured values from your DC sweep aren’t liningup with your XY mode results, you should recheck your setup and values.Matlab Plot6.LABORATORY: STEPFIVECompare the measured data to a simulation of the circuit, using the LTSpice circuit simulator anda premade example circuit. Run the example and upload a screenshot of the circuit. You shouldsee that the shape matches the XY plot saved above.1.Go to Canvas and download the LT spice circuit file (‘MOSFET_CIRCUIT_1.asc’)2.Open the circuit in LTSpice either using your own computer (download) or the labcomputers.3.Run the circuit simulation and insert a screenshot of the output plot below.a.Click File>Open and navigate to where the file is located and open itb.Right click on the background and click “run” or select the run from the menu anda blank plot should appearc.Left click the node labeled vout and the plot will update to show Vout vs Vin9 of 11

EECS 215Laboratory 2 –Speakerd.To optionally shift the plot to better match the recorded curve, right click on thebottom text and change the threshold voltage (VTO=1.9) before running thesimulation again. Feel free to experiment with this value.e.If you’re having trouble or want more instruction, go to discussion onThursday(10/12) for an introduction to LTSpice and an example of building andsimulating a circuit.LTSpice Screenshot4.Optional (not required): save your LTSpice data as a .txt file and include it in your Matlabplot in step four.a.File>export data as txt>V(Vout)>OkJust For Fun (not required):sweep through different frequencies, and determine the lowest andhighest frequency at which you can hear the speaker! Also try tuning the potentiometer to adjustthe gain of the amplifier (volume).You can also repeat the audio experiments using a 47Ω rather than 470Ω current limiting resistor(you’ll get more volume from the speaker).10 of 11

EECS 215Laboratory 2 –Speaker11 of 11