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Frequency Response of Transistor Amplifiers Lab Report ( WELL WRITTEN )

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Lab #3 Frequency Response of Transistor Amplifiers [Your Name] Bench #[--] ECE3120 Electronics II Date submitted: [--/--/--] Due date: [--/--/--]This lab is about getting understanding with the BJT amplifiers. In this lab two types of BJT configuration is discussed common-base and common emitter, how to use BJT in mid band and how to biased it at mid band. Also common-emitter and common-gate frequency response, low and high cutoff frequencies, and concepts of multistage amplifiers are explored. All the inputs and output waveforms are recorded and calculations are shown in measurement section. II. EQUIPMENT The following equipment was used for this lab, details are given below: Table 1. Equipment Used Equipment Type Details Oscilloscope Make: Agicent Technologies Oscilloscope was utilized to observe and measure the waveforms for calculation and analysis purposes. Model: DSO 1002A Serial Number: CN52438269 Digital Multimeter Hand Held Make: Fluke The DMM hand held was used to measure the voltage, resistance and the current. Model:45 Dual Display Multimeter Serial Number: 7560052 Analog Discovery Analog discovery’s function generator was utilized for the measurements and the observations Digital Multimeter Bench The DMM bench was used to measure the resistance, voltage and the current. Power Supply(Dual) Power supply was used for a constant voltage and current Resistor Decade Box On the lab bench, there was a resistor decade box for using different resistor.The following components was used for this lab, details are given below: Table 2. Components Used Qty Value Component Type 2 1 μF 25V electrolytic capacitor 1 10 μF 25V electrolytic capacitor 1 100 μF 25V electrolytic capacitor 1 2N3904 Transistor 4 2N3906 Transistor 1 100 Ω Resistor 1 1k Ω Resistor 1 2.2k Ω Resistor 1 3.3k Resistor 1 4.7k Resistor 2 10k Resistor 2 100k Resistor 1 470k Resistor 1 +/- 12volts Power BRICK III. INTRODUCTIONThe main concept of this lab is how to amplify a signal using BJT in common emitter and common gate configuration. Common emitter configuration of BJT is similar with common source configuration of MOSFECT’s. Simple operation is that when a small signal is superimposed on the DC bias at the base terminal in common emitter configuration then transistor will amplify it, and output is taken from collector terminal of BJT transistor. BJT is current control voltage device its output depends upon (ß) beta. We know that (ß) beta is current gain we have to configure transistor according to this parameter, beta is depend upon transistor it varies from transistor to transistor. ßDC = Ic / Ib …………… (1) ßAC = ∆Ic / ∆Ib …………… (2) In common emitter configuration: • The sinusoidal source voltage causes the base voltage to vary sinusoidally above and below its dc bias level. • The variation in base current produces a larger variations in collector current. • As the sinusoidal collector current increases the collector voltage decreases. • The collector current varies above and below its Q point in phase with the base current. Analysis: VC =VCC- ICRC …..……… (3) VCE =VC- VE .....………… (4) IE =VE/RE ……………… (5) VB = (R2 / R1+R2) VCC …. (6) IE = IC+ IB …………….. (7)IB = VBB - VBE / RB ……….. (8) Ic = ßIB …………………… (9) The sinusoidal collector to emitter voltage (Vce) varies above and below its Q point 180° out of phase with the base voltage. The CB amplifier is used to amplify only voltages it provides high voltage gain with a maximum current gain of 1. In common base configuration:

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