Week 2 Lab Assignment_UJT Operation (OL)

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EET 220 Industrial Applications Professor D. Overbye Week 2 Lab 3 “Uni-Junction Transistor (UJT) Operation By: Deandre Wheelington ECPI University I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial Review Board for determination. I will report to a Judicial Review Board hearing if summoned. Name Deandre Wheelington Date: 18 Nov 23

Abstract: In this lab, we will construct two separate circuits. In the first circuit, we will determine the measured voltage and current values at the anode of a transistor. In the second lab, we will measure and analyze the frequency of our transistor’s waveform’s using an oscilloscope when adjusting different resistance and capacitance values. Introduction: To start with the first lab, we will be measuring the voltage and current values at the anode of transistor by adjusting a potentiometer in our circuit. This potentiometer will show how added resistance at the anode of a transistor affects the current flow of the circuit thus affecting the flowing voltage amount. Once all values are recorded with given inputs, we will then plot these values on a graph to create a visual representation of our data. In the second lab, we will measure the frequency of a transistor’s waveforms and the difference in waveforms depending on how much resistance and capacitance is added to the circuit.

Lab 3 - Uni-Junction Transistor (UJT) Operation Objectives: 1. To verify and plot the switching characteristics of UJT. 2. To demonstrate the operation of UJT as a relaxation oscillator. 3. To Measure the frequency of oscillations. Procedures: Part I: UJT Characteristics:

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1. Construct the circuit as shown in the figure 1 using multisim. Q1 2N6027 R5 500Ω Key=A 0 % R3 470Ω R4 470Ω R1 15kΩ R2 51kΩ V1 9V Transsitors >> UJT >> 2N6027 PR4 A I: -- I(p-p): -- I(rms): -- I(dc): -- I(f req): -- PR1 V V: -- V(p-p): -- V(rms): -- V(dc): -- V(f req): -- 2. Adjust the R 5 potentiometer to 0%. 3. Place current and voltage probes at the anode of the UJT as shown above. 4. Run the simulation and fill the following table by varying the potentiometer as listed under column 1. Voltage Probe Current Probe Figure 1: UJT test circuit

Potentiometer setting V A I A 0% 901 nV -2.05 pA 10% 900 mV 0 A 20% 1.80 V 3.48 pA 30% 2.70 V 6.25 pA 40% 3.60 V 9.02 pA 50% 4.05 V 11.8 pA 60% 5.40 V 14.6 pA 70% 6.30 V 17.3 pA 80% 7.20 V 1.11 nA 85% 4.07 V 6.70 mA 95% 4.63 V 7.93 mA 100% 4.95 V 8.62 mA Table 1: Measured voltage and current values at the anode 5. Compare the values of V A and I A before and after firing (firing implying when UJT is ON). a. Prior to firing, as the V A increases I A increases until a voltage called as the peak voltage. From table 1, the peak voltage is 7.20 V b. After firing, I A continues to increase whereas V A drops to a lower value called as the valley voltage. From table 1, the valley voltage is 4.07 V . c. Since voltage decreases when current increases, this region of operation of UJT is referred as negative resistance region. 6. Based on the readings from the table 1, plot the graph between Anode current (I A ) on X-axis and Anode voltage (V A ) on the Y-axis. Note: Use word or Excel to plot the graph. Properly indicate the titles for each axis.

Part II: UJT as Relaxation Oscillator 1. Modify the previous circuit as shown below.

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Q1 2N6027 R4 20Ω R1 16kΩ R2 27kΩ V1 9V R3 47kΩ C1 0.1µF XSC1 A B Ext Trig + + _ _ + _ Anode Gate Cathode PR1 V V: -- V(p-p): -- V(rms): -- V(dc): -- V(f req): -- Figure 2: UJT Relaxation Oscillator 2. Record the frequency of oscillations in the table below by modifying the values of R 3 and C 1 as listed below. Use the voltage probe to measure the frequency. R 3 C 1 Measured Frequency 47k Ω 0.1 µF 192 Hz 68k Ω 0.1 µF 133 Hz 75k Ω 0.1 µF 121 Hz 75k Ω 0.01 µF 1.14 kHz 91 k Ω 0.01 µF 944 Hz Table 2: Measured frequency values 3. Connect the oscilloscope at Anode, cathode and gate and insert the waveform snippets (at least 3 cycles) for each of the terminal below using the values in the first row of table 2.

Experiment Questions: 1. After UJT fires, V A decreases, and I A increases. a. Increases b. decreases 2. A positive pulse train is found at the Anode of a UJT oscillator a. Anode b. Cathode c. Gate 3. The voltage waveform at anode is a sawtooth. a. Anode b. Cathode c. Gate 4. If the value of R E increases, the oscillator frequency decreases. a. Increases b. decreases Conclusion: To conclude this lab, we determined that adjusting a resistance potentiometer in our first circuit, determines the voltage and current values of our transistor. Given predetermined values of our potentiometer made plotting the outcomes simple and concise. We created a graphical representation of live voltage and current data to display how a UJT transistor triggers itself once it receives a peak voltage. After this peak voltage is activated, we then noticed that the ujt’s amperage continued to rise as the voltage dropped. This tells us that the UJT is still self-sustaining at its minimum “valley voltage”. In our second lab, we measure different frequency’s of waveforms of a UJT acting as a relaxation oscillator. This allowed us to determine how added resistance or capacitance can shift the waveform of a UJT transistor. SOURCES: Bartelt, T. L. (2011). Industrial Automated Systems: Instrumentation and Motion Control. Cengage Limited. https://ecpi.vitalsource.com/books/9781305474277