Clemson ECE Laboratories - Electronics Lab Information
Explore pre-labs for ECE 311 Electronics Lab I, created by Steven Chambers in Fall 2012 at Clemson University. The labs cover topics like curve tracer plots for diodes and transistors, background on Bipolar Junction Transistors (BJTs), instructor and lab coordinator contact information, mandatory safety video, and preparations using B2SPICE circuit simulation software for the next week's lab.
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Clemson ECE Laboratories 1 ECE 311 Electronics Lab I Pre-labs for ECE 311 Created by Steven Chambers in Fall 2012 Last Updated: 12/20/2012
Clemson ECE Laboratories 2 LABORATORY 0 LABORATORY DEMONSTRATION
Clemson ECE Laboratories 3 Introduction to Laboratory 0 Curve Tracer Plots I-V curve for two and three terminal devices Can plot a family of curves for different bias conditions Used in this lab to give characteristics of diodes and transistors Current/Voltage/Power limitations used to prevent destruction of device under test (DUT)
Clemson ECE Laboratories 4 Background Information Bipolar Junction Transistor (BJT) Three terminal device (Emitter, Base, Collector) Base current controls Collector-Emitter current I-V curve Y-axis: IC X-axis: VCE Family of curves represents different IBvalues As IBincreases, ICincreases for the same VCEvalue
Clemson ECE Laboratories 5 Contact Information Instructor: Name: Email: Office: Phone: Office Hours: As needed (email for appointment) Lab Coordinator: Name: Dr. Timothy Burg Email: tburg@clemson.edu Office: 307 Fluor Daniel (EIB) Phone: (864)-656-1368
Clemson ECE Laboratories 6 Mandatory Safety Video
Clemson ECE Laboratories 7 Preparations for Next Week B2SPICE Circuit simulation software Uses computer models to predict circuit behavior All parts used are considered ideal Observed value will differ from simulated value, but still good estimation Tests most often used in this lab are DC Sweep, Transient testing, and frequency sweep DC Sweep used for both simulations of next weeks lab
Clemson ECE Laboratories 8 Preparations for Next Week For Part 2: Click Sweeps tab under DC Sweep Then click Set up Sweeps The dialogue to the right will appear. Use these settings to properly sweep the R from 100 to 1000 to 10k ohms.
Clemson ECE Laboratories 9 LABORATORY 1 DIODE CHARACTERISTIC
Clemson ECE Laboratories 10 Introduction to Lab 1 Diode Allows current to flow in one direction under forward bias rd dynamic forward resistance rd = VD/ ID (reciprocal of I-V slope) RD static forward resistance RD = VD/ID V cut-in voltage point where appreciable current conduction begins n ideality factor dependent upon physical characteristics of diodes VBR breakdown voltage IS reverse saturation current current that flows under reverse bias VT thermal voltage = 0.0285V at room temperature - VD + ID
Clemson ECE Laboratories 11 Diode Characteristic Part 1A will replicate forward bias on curve tracer Part 1B will replicate reverse bias on a Zener diode Zener diodes have a lower VBR because they are designed to keep a constant voltage drop across it
Clemson ECE Laboratories 12 Ideality Factor The ideality factor, n, depends on the type of semiconductor material used in the diode, the manufacturing process, the forward voltage, and the temperature. Its value generally varies between 1 and 2. For voltages less than about 0.5 V, n ~ 2; for higher voltages, n ~ 1. (experiment shows values typically 1.15 n 1.2) The ideality factor, n, can readily be found by plotting the diode forward current on a logarithmic axis vs. the diode voltage on a linear axis.
Clemson ECE Laboratories 13 Finding Ideality factor, n Pick two points where currents are 10 times different Find ?? = ? ?? ??? = ln 10 = 2.3 ??= 0.0258 ? ??= 2.3 ? ?? ??= 2.3 ? ??= 2.3 ? 0.0258 = 0.0593 ? = ? 59.3 ?? ?? ? = ??.???
Clemson ECE Laboratories 14 Cut-in Voltage V : 0.4V to 0.7V for silicon 0.2V to 0.4V for germanium If the applied voltage exceeds V , the diode current increases rapidly.
Clemson ECE Laboratories 15 Diode Resistance Three diode resistances are commonly calculated: DC or Static forward resistance, RF or RD AC or Dynamic forward resistance, rf or rd Applying the diode equation and differentiating Reverse resistance, rr the reciprocal of the slope of the reverse characteristic, prior to breakdown
Clemson ECE Laboratories 16 Junction Capacitance of Diode ( Cj )
Clemson ECE Laboratories 17 Experiment: Measurement of diode characteristics Forward I-V Characteristic Use the curve tracer to obtain the forward characteristics of the silicon 1N4004 diode. follow the steps mentioned in lab manual for selecting Vmax =2V, Imax = 2mA and Pmax =0.4W Fill out table 1.1 and perform calculations to find RF and rd
Clemson ECE Laboratories 18 Reverse I-V Characteristic Use Zener diode (this one looks transparent) Note the reverse breakdown voltage (around -14.6V)
Clemson ECE Laboratories 19 SIMPLE DIODE CIRCUIT Build the circuit Measure the output voltage, V0 Vary the Vin from 0V to 5V for R= 100 change R = 1k and 10k Fill out table 1.2
Clemson ECE Laboratories 20 Preparations for Next Lab Post Lab 1 All questions under Lab Report section (Part 1 and Part 2) should be answered Pre Lab 2 Figures 2.3 and 2.5 will be simulated Use a sinusoidal voltage source set to 60 Hz and 4 volt amplitude (8 V peak to peak) Run transient test for 4 periods (f = 60 Hz T = 1/f start time = 0)
Clemson ECE Laboratories 21 LABORATORY 2 POWER SUPPLY OPERATION
Clemson ECE Laboratories 22 Half-wave Rectifier Diode forward biased for Vin > V Diode reverse biased for Vin < V Allows current to conduct for roughly half of AC cycle Vm = Vp - V
Clemson ECE Laboratories 23 Full-wave Rectifier D2 and D3 forward biased when Vin > 2V D1 and D4 forward biased when Vin < 2V Vm = Vp 2V Output frequency is twice that of input Output does not share common ground with input
Clemson ECE Laboratories 24 Filtering Adding a capacitor in parallel with load resistor creates a filter Capacitor will charge up on first half of cycle then discharge slowly based on capacitance This creates a voltage source with ripple Vr = Vm Vmin
Clemson ECE Laboratories 25 Preparations for Next Lab Post Lab 2 3 questions under Lab Report Pre Lab 3 First Design Lab I will split the class. Half the class will come for the first hour. Other half will come for the second. Bring your design calculations with you to lab Please print ECE 311 Lab 3 Lab Summary page from lab manual and bring with you to next lab. This will be turned in as your post lab prior to leaving lab next week.
Clemson ECE Laboratories 26 LABORATORY 3 POWER SUPPLY DESIGN
Clemson ECE Laboratories 27 Power Supply Design Calculations This lab is to be completed individually Remember Vin is measured after the source resistor Rs Fill out Lab Summary sheet and turn in before your leave
Clemson ECE Laboratories 28 Preparations for Next Lab Pre Lab 4 Simulate circuits 4.5(a) (Vb = 0 and 2 V), 4.6(a) (Vb = 0 and 2 V), 4.7, and 4.8 There is an error in the prelab statement. DO NOT SIMULATE FIGURE 4.4(a). Lab Report: You are to complete a formal lab report on your choice of Lab 1-3. You have 2 weeks to complete the report. It is to be submitted electronically before 5 PM on 10/9. Follow report format in the lab manual and look to the rubric uploaded on blackboard to see how it will be graded
Clemson ECE Laboratories 29 LABORATORY 4 DIODE CLIPPERS AND CLAMPERS
Clemson ECE Laboratories 30 Clipper Circuit that limits the output voltage to either an upper or lower limit (or both) through the use of diodes and voltage sources Diode begins conducting and holds output to a desired level (V + V in the configuration seen below) Diode and battery orientation determine whether circuit is positive or negative clipper
Clemson ECE Laboratories 31 Clamper Circuit that shifts the DC value of an input voltage through the use of a diode and capacitor Diode conducts on negative half cycle to allow capacitor to charge Once charged, capacitor passes AC signal shifted by the charge built on C Diode polarity determines positive or negative clamping (positive pictured below) RC time constant must be much larger than input signal period
Clemson ECE Laboratories 32 Note on circuit connection The NI-Elvis VPS is internally grounded This means no physical wire connection on your board is required to ground the voltage source Connection already made within NI-Elvis board For Vb = 0, connect diode straight to ground For non-zero Vb, connect diode to VPS supply + or supply -
Clemson ECE Laboratories 33 Preparations for Next Lab Post Lab 4 3 questions under Lab Report Pre Lab 5 Be familiar with BJT transistor operation and read through lab I do not require you to bring in graph paper Remember: Lab report due next week
Clemson ECE Laboratories 34 LABORATORY 5 BIPOLAR JUNCTION TRANSISTOR CHARACTERISTICS
Clemson ECE Laboratories 35 Bipolar Junction Transistor Three terminal device: Collector, Emitter, Base Collect-Emitter current controlled by B-E current Four regions of operation {NPN (PNP)}: Cutoff Both P-N Junctions reverse biased Saturation Both P-N Junctions forward biased Forward Active B-E (B-C) forward biased, B-C (B-E) reverse biased Inverse Active B-E (B-C) reverse biased, B-C (B-E) forward biased N P P N P N
Clemson ECE Laboratories 36 Output Characteristic Forward Active Saturation Cutoff
Clemson ECE Laboratories 37 Transistor Parameters hFE = IC/IB = dc current gain hfe = IC/ IB = o small signal (ac) current gain hie = VBE/ IB = r input resistance hoe = IC/ VCE output conductance hre = VBE/ VCE voltage feedback ratio hie can be approximated from VT/ICQ VA Early Voltage
Clemson ECE Laboratories 38 Preparations for Next Lab Post Lab 5 6 questions under Lab Report Pre Lab 6 Figure 6.2 DC Sweep to find Q point Figure 6.1 Transient analysis for various R Use transient setup given in pre lab Remember: Electronic copy of lab report due tonight by 5 pm
Clemson ECE Laboratories 39 LABORATORY 6 BJT COMMON-EMITTER CIRCUIT BIAS
Clemson ECE Laboratories 40 Common Emitter Bias Circuit Emitter is used as a reference point for both input and output R1 and R2 form a bias network to set a desired base current RC used to set output voltage levels RE helps reduce circuit variation with but also reduces AC voltage gain
Clemson ECE Laboratories 41 Q-Point Bias circuit is used to select an operating (Q) point Q point should be well into the forward active region to get a properly behaving amplifier circuit When adding a small signal AC voltage, the output voltage will shift with the AC input based on gain If the Q point is too close to saturation or cutoff, output waveform will distort and circuit will not behave as a proper amplifier
Clemson ECE Laboratories 42 Common Emitter Amplifier AC input signal can be added to base terminal (C1 used to filter out any DC component) VO is takes from collector terminal to ground (C2 once again used to remove DC component) CE added to increase AC gain; Emitter is shorted to ground for AC We will explore this more next week in Lab 7
Clemson ECE Laboratories 43 Preparations for Next Lab Post Lab 6 4 questions under Lab Report Pre Lab 7 Simulate circuit 7.1 for the 10 different configurations given in the lab manual
Clemson ECE Laboratories 44 LABORATORY 7 BJT COMMON-EMITTER CIRCUIT VOLTAGE GAIN
Clemson ECE Laboratories 45 Common Emitter Amplifier Once Q point is established, small AC signal can be added to base This signal is amplified and seen at the collector terminal
Clemson ECE Laboratories 46 Hybrid- Equivalent Circuit Used to model BJT response to small signal AC input gm = ICQ/VT Ro = VA/ICQ R = /gm When applied to overall circuit, can provide small signal voltage gain from input vs output transfer function
Clemson ECE Laboratories 47 Effect of Emitter Capacitor With CE: Without CE: With CE, two sides of circuit only share a common ground; without CE, RE adds a feedback loop which produces a voltage divider, reducing V and the gain
Clemson ECE Laboratories 48 Frequency Response Capacitors in this circuit have been selected so they essentially provide 0 impedance at circuit operating frequency. As frequency is changed, the capacitors start to produce an appreciable impedance; thus, lowering the gain of the circuit.
Clemson ECE Laboratories 49 Preparations for Next Lab Post Lab 7 4 Questions under Lab Report Pre Lab 8 2 Hour group design lab Each student should read through and do design calculations individually and perform simulations Lab Report 2: Due 11/13 by 5:00 PM, electronic submission Pick from Labs 4-7
Clemson ECE Laboratories 50 LABORATORY 8 BJT COMMON EMITTER DESIGN I
