MSCI 222C Class Readings Schedule. MSCI 222C - Electronics 10/12/ Class Seating Chart Mondays Door Cabinet Electronics Cabinet

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1 Class Seating Chart Mondays Door Electronics MSCI 222C Fall 2018 Introduction to Electronics Charles Rubenstein, Ph. D. Professor of Engineering & Information Science Session 6: Mon/Tues 10/15/18 & 10/09/18 (H5,Q4,L3) Mondays 1:00-3:50pm; Tuesdays 2:00-4:50pm ARC E-13 1 MONDAY 1pm Sitai Justin Jordan Itahy Jane David Emmy Thirteen Ava Luke Toni Aidan Jingyi Khalil Instructor Station Whiteboard and Screen Class Seating Chart Tuesdays TUESDAY 2pm Electronics Door Jairo Yeri Yide Danni Elaine Brandon Leo Andy Stephanie Instructor Station Whiteboard and Screen 3 MSCI 222 Fall Class Schedule & Due Dates MONDAY TUESDAY NOTES 27 August 28 August Session 1. Introduction, Review of Syllabus, Basic Concepts 3, 10 September 11 September NO CLASSES Labor Day / Instructor Unavailable 17 September 4 September Session 2. Basic Electronic Devices (Homework #1 Due) 24 September 18 September Session 3. Semiconductor Materials & Semiconductor Diodes (H2, Q1,L1) 1 October 25 September Session 4. Decimal and Computer Number Systems (H3, Q2,L1) 8 October 2 October Session 5. Transistors as Switches and Amplifiers (H4, Q3,L2) 15 October 9 October Session 6. Analog and Digital Concepts (H5, Q4. L3) 16 October NO Tuesday CLASSES Midterm Break 22 October (*) 23 October (*) Session 7. The Operational Amplifier (H6, Q5, L4) 29 October(**) 30 October (**) Session 8. Digital Integrated Circuit Logic Gates (H7, Q6, L5) 5 November (***) 6 November (***) Session 9. Flip-Flops & "Clocks" (H8, Q7, L6) 12 November 13 November Session 10. Digital Counters (H9, Q8, L7) 19 November 20 November Session 11. Digital Shift Registers (H10, Q9, L8) 26 November 27 November Session 12. Using Analog and Digital IC Circuits Together (Q10, L9) 3 December 4 December Session 13. Interfacing Computers; RFID Last Day for Labs (L10) 10 December 11 December In-class 2.5 hour Final Examination NOTE: 5-minute Quizzes one week after homework due & reviewed session MIDTERM: (*) Distributed; (**) Exam/Draft Paper Due; (***) Reviewed in class In-class Final Exams 10/11 December (Monday 10 December = Conflict Day) 4 MSCI 222C Class Readings Schedule In addition to the Class Notes (222Notes.pdf)!!! Session Due Notes 2 EW1: Pp 1-27; Armstrong: Chapters 1 3 (Pp 1-16) 3 EW1: Pp 28-65; Armstrong: Chapters 4 6 (Pp 17-63) 4 EW1: Pp 66-76; Armstrong: Chapters 7 9 (Pp ) 5 EW1: Pp 77 -End; Armstrong: Chapters (Pp ) 6 EW2: Pp 1-50 and Pg 90; Armstrong: Chapters (Pp ) 7 EW2: Pp 51-79, Review Pg 12; Armstrong: Ch. 14 End (Pp ) 8 EW2: Pp 80 - End, Review Pg 12 (CD4013, CD4017) 9 EW2: Review Pg 12 (CD4013, CD4017) 10 EW2: Review Pg 37 (555 Timer) 11 Review EW1 and EW2 as necessary, Sensors Lab Manual if interested 12 and on Review EW1 and EW2 as necessary EW1 = Basic Electronics: Transistors and Integrated Circuits, Workbook I by Forrest M. Mims, III (ew1.pdf) KEY EW2 = Digital Electronic Projects, Workbook II by Forrest M. Mims, III (ew2.pdf) Armstrong = Man of High Fidelity (armstrong2.pdf) Sensors = Radio Shack Electronic Sensors Lab by Forrest M. Mims, III (sensors.pdf) 5 MSCI 222C Hands-on Lab Modules #01: Measuring Resistance and Voltage #02: Voltage Sources, LEDS, Diodes & Characteristic Curves #03: Capacitors, Time Constants & Transistor Gain #04: Voltage Regulation & Transistor Switching #05: Analog IC Voltage Comparator #06: Basic Digital Logic #07: Set-Reset Latches & Type D Flip-Flops #08: Decade Counter and One Shot Switch Debouncer #09: Three Stage Type D Flip-Flop Shift Register #10: NE555 IC Timer Circuits Optional Labs (Additional Labs may be added or substituted): #A: Sound Detector Circuit (Audio-triggered One-shot) #B: Seven Segment Display Decoder-Driver Circuit 6 1

2 Instructor Contact Information Dr. Charles Rubenstein Professor of Engineering & Information Science Pratt Brooklyn Campus Office: ARC G-49 Fall 2018 Office hours (by appointment *) Mondays: 4:00pm - 5:00 pm = ARC G-49 (or E-13) Tuesdays: 5:00pm - 6:00pm = ARC G-49 (or E-13) (*Please me at least a day in advance if you plan on coming to office hours ) Send me an crubenst@pratt.edu Subject line: 222C or Electronics 7 * Class Session Archives 18fa06.pdf (Class PowerPoint slides)* 18fa06_h.pdf (6-slide/page handout format)* *Power points normally available by Wednesday evening After last class of the session 8 Fall 2018 Tutoring Sessions Fall OPEN LAB TIME - ARC E-13 Mondays 9am - 1pm Wednesdays 12 noon - 5pm Thursdays 12 noon - 5pm Fridays 9am - 5pm BY PRE-ARRANGEMENT ONLY CONTACT: Mrs. Margaret Dy-So, Assistant to the Chairperson Mathematics & Science Department ARC G-41 On pre-arranged day, access to E-13 and the White Console is obtained from Ms. Dy-So or the student assistant in room G Today s Class - Session #06: DUE: Homework Set #05 Readings: Electronics Workbook 2 (ew2.pdf): Pp 1-50 & page 90 Armstrong: Chapters (Pp ) Lecture: Analog and Digital Concepts 2 Do: Quiz #04, Review Homework Set #05, Lab #02 Module #03: Capacitors, Time Constants & Transistor Gain For Session 7: Operational Amplifiers (Op Amps) DUE: Homework Set #06 Readings: Electronics Workbook 2 (ew2.pdf): Pp 51-79, 12 Armstrong: Chapters 14-end (Pp ) To Do: Quiz #05, Review Homework Set #06 and Lab #04, Module #04; Voltage Regulation & Transistor Switching Midterm Distributed October 22 & 23! 11 Questions? 12 2

3 MSCI 222C Electronics Review Kirchhoff s Laws - KCL & KVL Ohms Law Power Law emath Calculations Combining Resistors Time Constants Voltage Divider Equation Kirchhoff s Laws: KCL KVL KCL: The current going into any point has to be the same as the current going out of the point also called The Law of Conservation of Current KVL: The sum of all the voltages, as you go around a circuit from some fixed point and return there from the opposite direction, and taking polarity into account, is always ZERO also called The Law of Conservation of Voltage OHMS LAW & the POWER LAW There are three common forms for each Equation: Ohms Law: V=IR V = I R R = V / I I = V / R Power Law: P = I V P = I V P = I (IR) = I 2 R P = (V/R) V =V 2 /R About Electronics Math Calculations Ohms Law equation: V=IR and I = V / R 1. If R is 1 Ohm = 1 Ω and V is 1 volt: then I = 1 Ampere 2. If R is 1MΩ = 1,000,000 Ω and V is 1 volt: then I = 1 microampere = (1 ua = 1 µa) 3. If R is 1k Ohm = 1kΩ = 1000Ω and V is 1 volt: then I = 1 milliampere ( = 1 ma) This is the most common calculation for our labs Series Resistors Parallel Resistors 1. Resistors in SERIES add R ab = R 1 + R R n 2. For n Like Resistors in SERIES: R ab = n R 1. The Inverse of Resistances in PARALLEL add 1/R ab = 1/R 1 + 1/R /R n 2. For TWO Resistors in Parallel; R ab = R 1 R 2 / (R 1 + R 2 ) 3. For n Equal Resistances in Parallel; R ab = R / n

4 Simple Series/Parallel Resistor Circuits R ab a b The Equivalent Resistance of the circuit above: R ab = [ R 1 R 2 / (R 1 + R 2 ) ] + R 3 19 Time Constant NOTES The time required to charge or discharge a capacitor requires calculating: τ = R C With: τ in seconds, R in ohms, and C in Farads 20 Diodes in Series Circuits The Voltage Divider Equation When a resistor (R 1 ) and a diode are connected in series to a voltage source (V) we use KCL to realize the current is the same through all series elements. Using the standard forward voltage drop (V d ) value of 0.6volts and Ohm s Law we find the current through the resistor. For V = 15 and R 1 = 1KΩ : I R = I d = (V - V d )/R 1 = (15-0.6) volts / 1KΩ I R = 14.4 volts / 1K = 14.4 ma 21 Vout = Vin [ R 2 / (R 1 + R 2 ) ] When a voltage is applied to two (or more) resistors in series, the voltage across a particular resistor is the applied voltage times the selected resistor divided by the sum of the resistors 22 Transistor Circuit Voltage Dividers Transistor Base Voltage Divider Network About Transistor Calculations The NPN schematic symbol can be divided into: 1. An Base-Emitter INPUT circuit where the base-emitter junction forms a silicon diode: and V be = V d 0.6v Vout = Vin [ R 2 / (R 1 + R 2 ) ] or Vb = V [ R 2 / (R 1 + R 2 ) ] And a Collector-Emitter OUTPUT circuit where: a. I C = I B h FE b. With I C limited by the saturation current calculated as if the C-E junction is a short circuit giving a maximum collector current possible: when the transistor is fully on (V CE 0) 24 4

5 NOTES: NPN Transistor Switch As shown, with switch DOWN: V in = 0 Voltage at the base, V b = 0 And the LED is OFF With the switch in the UP position: V in = +Vcc Voltage at the base, V b = V cc V R1 KVL: LED Voltage, V LED = V cc V R1 V be And the LED is ON NOTE: V CE zero apx short circuit when transistor is ON ) 25 Questions? 26 MSCI 222 Electronics Lecture Notes Module 6 Console Relay Layout The Relay coil power is applied to SPRINGS #57 and #58. Note that Connection #55 is spring-loaded and movable between connections #54 & #56. Relay Layout SPRINGS #54 & 55 create a NO (normally open) switch SPRINGS #56 & 55 create a NC (normally closed) switch COMMON NC NO About the Relay on the Console A Relay is merely a coil of wire around a iron core (inductor) that can be used to automate the switching of high voltages and/or currents with very small controlling voltages. It works on the principal of an electromagnet that becomes a magnet when current flows through the coils. UNFORTUNATELY, the relay s iron core retains some magnetism after the current stops flowing in it. Thus there is a pull-in voltage needed to overcome the spring holding the switch closed, and a dropout voltage level that must be measured and accounted for. 29 Buzzer Layout Console Buzzer Spring Layout 30 5

6 About the Buzzer on the Console Relay-type Buzzers, operate very much like a relay. However, when the coil is energized it opens the NC switch which interrupts the coil power. With the current stopped, no current flows through the coil which releases the switch reconnecting power to the buzzer s electromagnet, that pulls in the contact, releasing power, and so on, VERY QUICKLY. The on-off condition can be designed to produce a noise the buzz! (The buzz that occurs in normal relay operation is called Chatter ) Our console s buzzer is actually a piezoelectric device that produces a vibration when voltage is applied to it. MSCI 222 Electronics Module 6, Part 1 QUICK Concepts! Analog and Digital What do "analog" and "digital" really mean? How can an analog music waveform be converted into a digital file or compressed digital file (such as mp3)? Sampling at 22KHz or 44KHz what are the differences? In piezoelectric microphones the reverse action occurs where sound waves vibrate the crystal structure producing a small current. What do these concepts have to do with the binary number system and digital coding? MSCI 222 Electronics Module 6, Part 2 QUICK Concepts! Power Supplies & Voltage Sources What is the difference between a power supply and a voltage source? How does an UNREGULATED voltage source differ from a REGULATED voltage source? The 78xx series of voltage regulator integrated circuits are housed in transistor and power transistor packages and can be used to create POSITIVE regulated voltage sources (7812 = +12V, etc.) FYI: 79xx series devices create NEGATIVE regulated voltage sources (e.g., 7905 = -5V, 7912 = -12V) We ll see shortly how we can use a 7805 IC to create a +5V regulated voltage source. Copyright C.P.Rubenstein 33 The 7805 Voltage Regulator The 7805 Voltage Regulator IC is designed to provide a constant 5 volt output over a wide range of unregulated input voltages. The 7805 was designed to provide a regulated source of voltage to the TTL family of digital integrated circuits. It is ideal for powering any circuit that requires a stable +5 volt power supply. Our unit is in a TO-220 case without a heatsink. NOTE: The Part number on the device might be LM7805, KA7805, MC7805, L7805CV, etc. Unregulated Vin: +7.3 to +35 volts Regulated Vout: +5 volts (+/-0.2 v) Load Regulation: +/- 10 mv typical, max +/- 50 mv Peak Output Current: TO-220 case on a heatsink OR TO-3 metal case on a heatsink: up to 1 Ampere TO-92 plastic case: 100 ma Voltage Regulator Circuit Wiring the MC7805 Voltage Regulator as a 5 Volt Source Pins A1 B1 C1 on our breadboard See Lab Module We add a GREEN LED to verify power is ON! We ll keep this circuit wired for the rest of the semester! 35 Transistor Switching: Relay & Buzzer Circuit In today s lab we will also wire a transistor switching circuit, and see that a small change in base current (voltage divider voltage) results in closing the relay - sounding the buzzer This is a similar circuit to the one tested last week BUT now we use: R2 = 10,000 Ohms!!! The next slide shows how the base current, etc., may be calculated Copyright C.P.Rubenstein 36 6

7 Transistor Currents Since the Base-Emitter is a forward biased silicon diode with a 0.6 volt drop, we can approximate the base current I B by looking at KVL in the Base loop; V input = V R (base resistor) + V BE (which is 0.6 volts) V input -V BE = V R knowing the value of R, calculate I B : I B = [V input -V BE ] / R and if we know the transistor gain h FE we can calculate the collector current I C from: I B * h FE = I C MSCI 222 Electronics Homework #05 Transistor Circuits Review Homework 5.A Armstrong Questions Armstrong Reading Questions: 5.A1a) From your Armstrong readings recall the passage: "Sarnoff was furious. He issued an edict that anyone who allowed Armstrong to (???) again would promptly be fired." What did Armstrong do? Pp : He went out on the roof and to the top of the antenna tower to pose for a picture 5.A2) The signature by the Notary on Armstrong's crucial document appeared to be forged. What was the explanation? Pg. 130: The notary had two official signatures Homework 5.B1 5.B1 What would the collector current I C have to be if the base current I B is 0.02 ma? We are given h FE = 200 Recalling that I C = h FE x I B Thus I C = (200) (0.02 ma) I C = 4.0 ma =============================================== BTW: If I B = 0.02 ma, and R 2 = 100Kohms, V R2 = I B x R 2 = 0.02 ma 100K = 0.02E-3 100E+3 and V R2 = 2.0 volts Homework 5.B2 5.B2 What would the collector current I C have to be if the voltage from the potentiometer slider to ground is approximately 5.0 volts? Using KVL: V R1-G -V R2 -V BE = 0 V R1-G From which: V R2 = V R1-G -V BE Since V R1-G = 5.0 v and V BE = 0.6 v, V R2 = V R1-G - V BE = = 4.4 Volts Using KCL: I R2 = I B = I E I R2 = V R2 / R 2 = 4.4 Volts / 100Kohms = 4.4 E-5 A or ma I C = h FE x I B = (200) (0.044 ma) I C = 8.8 ma 41 Homework 5.B3 5.B3 If the base current is 0.2mA and h FE = 200 explain why the collector current I C will be much less than 40 ma. The collector current must be less than 16 ma because: a. The h FE equation calculates I C (saturated) I C = h FE I B I C = (200) (0.2 ma) I C = 40 ma ; b. BUT with a 1Kohm resistor in the collector circuit, Ohms Law states that the voltage drop across a resistor if the current flowing through it is 40 ma is: V CC = I R ; V = 40 ma 1K ohm = 40 Volts! c. However, we only have a 16 Volt input voltage: V CC = 16 v therefore the MAXIMUM current that can flow in the 1K Ω collector resistor R 3 is limited to 16V/1K = 16 ma! = less than 40mA! 42 7

8 Homework #04 Quiz Questions? Number Systems When you DO NOT show work, I have to guess. When you DO show work, I can try to see what you are doing and give an O.K MSCI 222 Electronics Hands-on Lab #02 Review: Voltage Sources, LEDS, Diodes & Characteristic Curves Parts Needed for Lab Module 2 Radio Shack Electronic Learning Lab Console, 9V AC Adapter, Wire Stripper, Colored Wire and Colored Alligator Clip Leads, Digital Multimeter * (* Used in all future labs) (1) 100,000Ω Resistors 100KΩ [brown-black-yellow-gold] (1) 10,000Ω Resistors 10KΩ [brown-black-orange-gold] (4) 1,000Ω Resistors 1KΩ [brown-black-red-gold] (1) 10,000Ω Potentiometer ( 10KΩ Pot on Console) (1) 1N4007 Rectifier Diode (1) Green LED Diode Lab Module 2: 1a, 1b, 2a VOLTAGE SOURCES 1.a) What is the voltage output of the 9V cube adapter? Apx volts (unregulated voltage, unloaded ) 1.b) What is the (10KΩ) loaded unregulated source voltage, V? Apx volts VARIABLE VOLTAGE SOURCES 2.a) What is the resistance of the 10KΩ potentiometer for V o = 5.0 volts? Apx 3.79 KΩ Lab Module 2: 3a 3c VARIABLE VOLTAGE SOURCES Add the LED into the circuit. The voltage at Spring #38 to ground V o is still 5.0 volts (unloaded) from last step. 3.a. What is the variable source voltage V o across the LED now? Apx 1.88 volts 3.b. Does the LED light up? _X_ Yes No 3.c. What is the lowest voltage, V o across the LED for it to light up? Apx 1.70 volts

9 Lab Module 2: 4a 4e Forward Biased Diode Circuit DISCONNECT THE 10K POTENTIOMETER! 4.a) Does the LED light? _X_ Yes No 4.b) What is the voltage measured across the LED V LED? Apx 2.11 volts Lab Module 2: 5 Reverse Biased Diode Circuit 5.a) Does the LED light up? Yes _X_ No 4.c) What is the voltage across the diode V d? Apx 0.67 volts 4.d) What is the voltage across the 1000 ohm resistor V R1? Apx 9.75 volts 4.e) What is the loaded unregulated source voltage, V unreg? Apx volts 5.b) What is the voltage across the reverse-biased diode? Apx volts Lab Module 2: Table 2.1 DIODE IV CHARACTERISTIC CURVE R 1 diode voltage (measured)* R 1 voltage (measured) current - ma (calculated) 100KΩ KΩ KΩ Ω (2@1K) 333 Ω (3@1K) 250 Ω (4@1K) (NOTE: I = V/R: V(volts) / R(Kohms) = I in milliamperes (ma) Be careful: The four 1KΩ paralleled resistors will get warm to the touch! this is Watts and these are 0.5 W devices!) 51 RESISTANCE Some Average Values Voltage across R1 (measured) Resistor Current in ma (calculated) Voltage across diode (measured)* 100K ohms 13.9 Volts 0.14 ma 0.51 Volts 10K ohms K ohms ohms* ohms* ohms* I = V / R (* 2, 3, or 4 each of 1K Resistors in Parallel ) The Diode s IV Characteristic Curve is shown on next slide 52 Diode IV Curve - Class Averages The values for a Diode s IV Characteristic Curve are obtained as we did in the lab and are then plotted where V= x; I= y. Questions? Note that with currents greater than 50mA the resistance of the diode (0.76/50mA) approaches 15 Ohms!

10 Today s Class - Session #07: DUE: Homework Set #06 Lecture: Operational Amplifiers (Op Amps) Readings: Electronics Workbook 2 (ew2.pdf): Pp 51-79, 12 Armstrong: Chapters 14-end (Pp ) To Do: Quiz #05, Review Homework Set #06 and Lab #04, Module #04; Voltage Regulation & Transistor Switching Midterm Distributed October 22 & 23! For Session 8: Digital IC Logic Gates DUE: HWK Set #07, Midterm & Paper March 19 & 20! Reading: EW2: Pp 80 - End, Pg 12 (CD4013, CD4017) 2 Do: Quiz #06, Review HWK Set #07 and Lab #04 Module #05: Analog IC Comparator MSCI 222 Electronics Hands-On Lab Module 3: Capacitors, Time Constants & Transistor Gain ** CAUTION ** Most electronic component leads have been tinned with a tin-lead coating to make them easier to solder into a circuit. Although we will NOT do soldering in this class, AFTER working with components, please avoid lead poisoning by washing your hands. Thank You! Basic Lab Notes 1) All measurements should be made with the Digital Multimeter in your Pratt Kit (Type KT-820B.or DT-830D). To conserve your multimeter s 9V battery, be sure to turn the meter off if not in use for over 5 minutes. Be sure to turn OFF all POWER before measuring Resistances 2) All work is to be done individually, and Results Sheets submitted when completed. Double check before you leave that your meter is turned off and in your Pratt kit. NOTE: There are no lab reports" in this course. 3) Enter all results on both the Instructions Sheet, and the Results Sheet. Keep the Instruction Sheets as a reference. Turn in the Results Sheets when you have finished the lab Inserting Components into a Breadboard Insert Resistors or Diodes and ICs across the notches Insert Transistors LM7805, or Resistors, parallel to the Notch Notch and connecting strips from underside of breadboard Parts Needed for Lab Module 3 Capacitors, Time Constants and Transistors (1) Red or Green LED (1) 2N5551 NPN Silicon Transistor (1) 100Kohm Resistor: brown black yellow gold (100KΩ at 5%) (1) 1000 Ohm Resistor: brown black red gold (1KΩ at 5%) (1) 100µF Electrolytic Capacitor The Radio Shack Electronic Learning Lab Console, AC Adapter (9 volts at 150 ma), Digital Multimeter, Wire Stripper, Miscellaneous Connecting leads and wires are REQUIRED for all future labs.)

11 CHARGING A CAPACITOR Lab Module 3 Connect a 100K ohm resistor to a 100 µf capacitor to the unregulated power supply to create the circuit of Figure 2. Note the minus sign on the side of the capacitor. The time constant Tau = RC for this circuit is calculated as 100E3 ohms times 100E-6 farads Thus: One Tau = 100,000 x = 10 seconds 61 Lab Module 3-3.1a 3.1b CHARGING A CAPACITOR Set the Multimeter to the 20V range. USE LAYOUT ON NEXT SLIDE Press the S1 push button switch to short the capacitor for a few seconds setting the V initial starting voltage to zero. Release S1 at t = 0. Record three (3) measurements for each test and then find the capacitor s average voltages at t = 10 and t = 50 seconds: 3.1.a) What is the voltage V c@ after one Tau = 10 seconds? 3.1.b) What is the voltage V c@5 after five Tau = 50 seconds? 3.1.c) What is the voltage V after at least two minutes? 62 Lab Module 3 Console Diagram CAPACITOR CHARGING CIRCUIT DPDT Switch UP. Push S1 to short capacitor, release, Measure, average three tests of times to charge capacitor to 10.0 volts S1 Lab Module 3 3.1c 3.1d Comparison to Theoretical Values: Theoretical value after one Tau = 63% of the supply voltage (V from 3.1.c). 3.1.d) What is the Actual % value at 10 seconds? [V c@ / V] x 100% = The theoretical value after five Tau should loaded supply voltage. 3.1.e) What is the Actual % value at 50 seconds? [V c@5 / V] x 100% = 5 63 We can expect our experimental values to be smaller than the theoretical values due to a non-infinite Multimeter resistance as well as leakage currents in the electrolytic capacitor. 64 Lab Module DISCHARGING A CAPACITOR Multimeter Internal Resistance Charge the capacitor to exactly 10.0 volts and then disconnect it from the circuit by removing the RED wire from T11 (connection to Spring #44). The capacitor voltage drop is now solely due to the load of the meter s internal resistance*. 3.2.a) How long does it take for the capacitor voltage to discharge to 3.7 volts? seconds (This is one Tau. If it takes more than two minutes there is an error) * NOTE: Removing the 100KΩ resistor will result in a time constant based on only the meter s resistance about 1MΩ. 65 Lab Module 3 Q6 6. Using the circuit of Figure 3.2 to once again charge the capacitor to exactly 10.0 volts This is the layout of the next slide with the DPDT Switch UP to charge and then DOWN to discharge with the capacitor directly across the 100K resistor as in Figure 3.3. Keep the capacitor discharging through the resistor for exactly 10.0 seconds and measure its voltage, before it has a chance to drop (use the average of three readings) 66 11

12 Lab Module 3 Console Diagram CAPACITOR DISCHARGING CIRCUIT Push DPDT Switch DOWN after charging Capacitor to 10.0 volts. 67 Lab Module 3 3.2b 3.2c Charge the capacitor to exactly 10.0 volts. Push the DPDT Switch DOWN. The theoretical value, after one Tau of discharging, would be 3.7 volts or 37% of the 10 volt initial value (Note: with a parallel 1M Meter resistance, R actual 90KΩ) 3.2.b) What is your experimental value of V c@ after one Tau? volts Charge the capacitor to exactly 10.0 volts. This time allow 5 Tau=50 seconds of discharge into the 100K resistor without meter connected. Then measure the capacitor voltage. We expect an answer near the final value, zero volts. 3.2.c) What voltage V c@5 did you find? volts This is Instructor check point 3A 68 Lab Module 3 3.3a 3.3b VARYING THE CURRENT IN THE TRANSISTOR BASE 3.3a) Turn the power ON and use the 10Kohm pot knob to adjust the voltage from 0 to full supply voltage. Did this work? ( YES NO) Lab Module 3 Part 4 Circuit 1 Measuring Transistor CURRENT GAIN (and possible circuit layout) 3.3b) Wire the full circuit shown. Using the 10Kohm pot knob, adjust the voltage available to the 100KΩ resistor in the transistor s base circuit to vary the brightness of the LED in the collector circuit. Did this work? ( YES NO ) This is Instructor check point 3B NOTE: the next slide has a possible layout for this circuit Numbers-only are spring connections A possible Console layout for the circuit above is shown at the left NOTE: Alpha-Numbers are Breadboard tie points Lab Module 3 Part 4 Circuit 2 Measuring Transistor CURRENT GAIN (and possible circuit layout) 71 Lab Module 3 3.4a 3.4c MEASURING THE CURRENT GAIN OF A TRANSISTOR READ THE LAB NOTES! Set V R3 to 5.0volts 3.4a) Measure the voltage V R2 across R 2 a 100Kohm resistor connected to the base. V R2 is: volts (measured). 3.4b) What is the base current, I B? ma (Calculate using Ohms Law [I = V/R] Remember V/Kohms = ma) 3.4c) Knowing the collector and base currents, use a calculator to find the current gain h FE = ( I C / I B )? h FE = (a number without units) This is Instructor check point 3C 72 12

13 Lab Module 3 3.4e 3.4f MEASURING THE CURRENT GAIN OF A TRANSISTOR Adjust the voltage across R 3, the collector resistor, to 5 volts, 2 volts and 1 volt to create collector currents of 5 ma, 2 ma and 1 ma. At each value of I c measure V R2 and V BE and calculate I B and h FE : I C V R2 I B (ma) = V R2 / 100K 5 ma V BE h FE Questions? 2 ma 1 ma Lab Module 3 CIRCUITS Numbers-only are spring connections Circuit 1. Measuring Transistor CURRENT GAIN Circuit 2. I C V R2 I B (ma) = V R2 / 100K 5 ma 2 ma 1 ma V BE Gain Measurements Table h FE Any Questions? Send me an crubenst@pratt.edu or c.rubenstein@ieee.org End