Assignment for Analogue Electronics (2017) 1 ASSIGNMENT Common Emitter Amplifier The purpose of this assignment is to study the performance of Common Emitter amplifier shown in Figure 1. It includes three parts: (1) Practical measurement (you have finished it in Lab 3), (2) Theoretical demonstration, and (3) PSPICE simulation. Figure 1 Vin C1=330n Polyester R1=56k R2=22k RB=180Ω CC=470p Polyester RC=4k7 Q1 BC337 RE=3k3 CE=220µ CL=10µ RL=1k VCC=+15V Figure 2 Part 1 Practical Measurement See Lab 3 sheets. B Vin C1=330n Polyester R1=56k R2=22k RB=180Ω CC=470p Polyester RC=4.7k Q1 BC337 Q2 BC337 RE=3.3k CE=220µ RE2 10k CL=10µ RL=1k A VCC=+15VAssignment for Analogue Electronics (2017) 2 Part 2 Theoretical Demonstration (1) As shown in Figure 2, for the left hand side of the dotted line AB of the circuit in Figure 1 calculate VB, VC, VE and IC (β=292). (2) Following Step 1, add C1, CE, CC and CL+RL load to the collector of Q1 and calculate the parameters for small signal equivalent circuit: rπ and gm, then the midband gain. (Hint: The behaviour of CC looks like the internal capacitance of transistor). (3) Calculate the high cut-off frequency using the high frequency equivalent circuit of transistor. (Hint: CC in the Figure 1 is much larger than the internal capacitance Cμ, so you can use CC to replace Cμ in the equation for the fH. You can also neglect Cπ). (4) Double the value of CC and repeat the calculation in Step 3, and find the change of the high cut-off frequency and bandwidth. (5) What are the changes of the high cut-off frequency and bandwidth if (i) CC is halved; (ii) CC = 0. (6) Change the value of CC to single one and add Q2 between the CL+RL load and the collector of Q1 as shown in the right hand side of the dotted line AB of the circuit in Figure 1. Calculate IC2 and gm2. (Hint: IB2 can be neglected and VC1=VB2). (7) Calculate the midband gain and bandwidth based on the following approximation: Q2 is an emitter follower, its voltage gain is about 1, and its input resistance is much larger than RC, so the total gain is approximately equal to the gain of common emitter amplifier (Q1). When you calculate the load resistance to obtain gain, please note the RC is much smaller than the input resistance of emitter follower. Part 3 PSPICE Simulation (1) Find the SPICE model for BC337 from the following web site and copy it into your PSPICE input file. http://web.rfoe.net:8000/ZILIAOXIAZAI/PHILIPS/models/spicespar/data/bc337.html Please note: You should use BC337-25. (2) Repeat all 6 steps in Part 1. In Step 4, you should add (i) CC is halved; (ii) CC = 0. Part 4 Results Analysis and Conclusion