lab3

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Florida Atlantic University *

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4361

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Electrical Engineering

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Feb 20, 2024

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EEL4119L Electronics Laboratory II Experiment 3 By Pablo Sanchez James Saville Niv Barazani Nabil Elsrouji Charles Florestal October 15, 2019

Group 5 Experiment 3 2 | P a g e Table of Contents Abstract ........................................................................................................................................... 3 Equipment and Tools Used ............................................................................................................. 3 Components Used ........................................................................................................................... 4 A. Class C Amplifier ................................................................................................................... 5 Procedure .................................................................................................................................... 6 ADS Simulations ........................................................................................................................ 8 Case A: Class C Amplifier Laboratory Measurements (Q=25) ................................................ 10 Case B: Class C Amplifier Laboratory Measurements (Q=34) ................................................ 13 Conclusion ................................................................................................................................ 14 B. 830KHz Colpitts Oscillator ...................................................................................................... 16 Introduction ............................................................................................................................... 16 Part 1: Open Loop 830KHz Colpitts Oscillator ........................................................................ 18 Procedure and Simulations ................................................................................................... 18 Part 2: Close Loop 830KHz Colpitts Oscillator ....................................................................... 22 Procedure and Simulations ................................................................................................... 22 ADS Simulations ...................................................................................................................... 22 830KHz Colpitts Oscillator Lab Measurements; Open Loop ............................................... 27 830KHz Colpitts Oscillator Lab Measurements; Closed Loop ............................................ 33 Crystal Controlled Colpitts Oscillator (PCB) ............................................................................... 35 Conclusion ................................................................................................................................ 42 Lab Report - Questions & Answers .............................................................................................. 43 Acknowledgment .......................................................................................................................... 47 References ..................................................................................................................................... 48

Group 5 Experiment 3 3 | P a g e Abstract Throughout this experiment, we will be making use of the oscillating properties of the LC circuits to make a Class C amplifier and a Colpitts Oscillator, each of which have their own unique property. For the Class C Amplifier, the BJT in the amplifier acts like a switch that when activated, would provide energy to an underdamped system (in this case the LC resonant circuit) and will continue to do so every ‘n’ cycle as opposed to a set frequency. For the Colpitts oscillator, the output of the Common Emitter amplifier, which is emitted at a phase shift of 180°, is transferred back into the input with the use of a feedback network that ultimately results in a 360° phase shift, creating a positive feedback loop. For this circuit, the oscillation rate is determined by the LC circuit. Equipment and Tools Used This experiment used different instruments and measuring tools accessible through FAU’s Electrical Engineering Lab room 210 in order to measure the passive component values, power the BJT Amplifier and measure and observe the behavior of both the Class C Amplifier and the Colpitts Oscillator. Furthermore, some additional tools were used to assemble one of the Colpitts Oscillator to a through-hole circuit board: • GW INSTEK GDM -8245 – Dual Display Digital Multimeter • GW INST EK GFG-3015 – Function Generator • GW INSTEK GPS -3303 – 3 Channel Laboratory DC Power Supply • Tektronix TDS 2012C – Two Channel Digital Storage Oscilloscope

Group 5 Experiment 3 4 | P a g e • Tektronix MDO3024 – Mixed Domain Oscilloscope • Tektronix TPP0250 - Voltage Scope Probe • Scope Probe • Banana Cable (BNC) to Pin • Voltmeter Probe • Soldering Iron • Solder • Wire Cutter/Clippers Components Used • ¼ W Resistors – Precision ±1% Metal Film • ¼ W Capacitors (Electrolytic, Multi -Layered Ceramic, Tantalum) • Inductors • 2N3904 & P N2222A NPN Bipolar Junction Transistor • Breadboard • Jumper Cable • Hakko 550 ֯ F Soldering Iron

Group 5 Experiment 3 5 | P a g e A. Class C Amplifier This experiment brings upon us a new component. The inductor has been theoretically studied by students in the past, but this will be the first time we get to physically handle them. This part of the experiment will teach us tuning of circuits to get the results we desire. We have been given design requirements with a specific circuit in mind. This circuit will include and inductor, resistors, and capacitors. They will form to build a Class C Amplifier. This amplifier should be displayed with the certain frequencies, resistances and capacitances to achieve certain Q values. Figure A1: Simple Class C Amplifier and Operating Curve (Amplifier Classes, 2019) Ideally this circuit should not dissipate any power, but in the real-world it dissipates enough energy to maintain efficiency. The transistor is the component that will do most of the dissipating since it will get surges of energy injected into it.

Group 5 Experiment 3 6 | P a g e Procedure The first step to beginning this project is to achieve the desired Q values. This will be done by calculating the resistor values at certain frequencies with certain capacitances. It requires building a circuit a simple RLC circuit with the resistor in line with the inductor and capacitor in parallel. It takes two-decade boxes: one capacitance and one resistance. This process involves tuning the frequency to get the input and output oscillations in phase. This means they will be at 0 degrees. The next step of tuning requires the output voltage exactly half of the input voltage by changing the resistance values with the decade box. The equation to calculate ? ? ∶ ? ? = 1 2𝜋√?𝐶 Then use the resistor values found from tuning and the ? ? to calculate the Q values using: ? = 2𝜋? ? ?𝐶 Table A1: Simple Class C Amplifier R and Q Values Nom+B5:G12inal C (Decade Boxes) Calculated fo f_0=1/(2π√LC) [Hz] Measured f0 [Hz] Measured C (decade boxes)[F] Measured Rs (decade boxes) [Ω] Calculated Q (from measured values) Q = 2pif0RC 17nf 55715.37 54300 1.7E-08 7200 41.7600602 15nf 59313.54528 58000 1.5E-08 8077 44.1518803 12nf 66314.55962 63700 1.2E-08 7600 36.5017881 10nf 72643.96 69920 0.00000001 5578 24.5052873 0.009uF 76573.46 72101 9E-09 6873 28.0227021 0.007uf 86826.14 83300 7E-09 7376 27.0236382 0.005uf 102734.07 92900 5E-09 7979 23.2870273 0.003uf 132629.12 113900 3E-09 9963 21.3902065 0.002uf 162436.83 138700 2E-09 10870 18.9459274 0.001uf 229720.37 173800 1E-09 13000 14.1962289

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