ECE 311 - Lab Page 1 of 8 ECE 311 - Lab Department of Electrical and Computer Engineering University of Idaho Title: Common-Base Amplifier Design Goal: To design, build, and test a Common Base Amplifier Preliminary: (Due at the beginning of the laboratory period) 1) Design a Common Base Amplifier to meet the following specifications: 1. VCC = 15V. 2. RL = 10kS 3. Ri = 50 S. 4. Av = 50V/V 5. RE $ 20re 6. VTH $ 5VBE (so IE is insensitive to VBE) 7. IRB2 = 0.1*IC (so IE is insensitive to $) 8. Standard 5% tolerance resistance values are used. Make the following assumptions: a. Let $ = 120 (you can also choose a $ based on your previous measurements) b. If RE $ 20re, Ri can be taken to be approximately re. 3) Determine the expected values of VB, VC, VE, IC, and Av for the amplifier using the standard values you ve chosen for the resistors. 4) Determine the expressions for, and the expected values of, both Ri and Ro for the amplifier. 5) Bring a copy of your calculations and expressions to use in the laboratory.
ECE 311 - Lab Page 2 of 8 VCC RB1 RC CC2 vo CB Q1 RS RL RB2 RE CC1 VS Figure 1 Common Base Amplifier Laboratory Procedure: 1. Construct the circuit in Figure 1 using the values selected in your design. Let CC2 = CB = 1:F and CC1=10:F. Measure the values of your resistors before you construct the circuit. For now, turn the function generator off (set v S = 0). 2. Measure VB,VC, and VE. From these values, you may determine IC, IB, and VBE, and from these calculations, you may approximate $ for your transistor. Record the values of VB, VC, VE, VBE, IC, IRB1, IRB2, and IB in the provided table. 3. Using your measured values in (1) and the value of $ and VBE from (2), calculate the following: VB, VC, VE, IB, IC, IE, IRB1, and IRB2. Record your values in provided table. 4. Using the DC calculations in (3) to determine the small-signal parameters for the BJT, calculate ve/vs, vo/ve, and vo/vs. Also, calculate the peak values for vo, vc, and ve. Assume v s = 10mV peak. Enter the values into the table. 5. Set v s = 10mV peak at a frequency of 10kHz. Measure the peak values of vo, vc, and ve. Use
ECE 311 - Lab Page 3 of 8 the oscilloscope to measure these voltages. Determine ve/vs, vo/ve, and vo/vs from these measurements. How do these values compare with the predictions? 6. From the DC calculations in (3), calculate Ri and Ro for the amplifier. 7. Measure Ri and Ro. This is measured with the same technique as for the common-emitter with emitter resistor amplifier built last week. Report: Please include a cover page, your data sheets with calculations, and a section on conclusions.
ECE 311 - Lab Page 4 of 8 1. RB1 - RB2 - RE - RC - RL - 2. DC Calculations and Measurements: Table 1 Voltage or Current VB VC VE VBE IC IRB1 IRB2 IB Measured value Calculated Value Calculated $
ECE 311 - Lab Page 5 of 8 3. Calculations for VB, VC, VE, IB, IC, IE, IRB1, and IRB2. 4. Table 2 Parameter Calculated Measured vo ve vc vo/ve ve/vs vo/vs
ECE 311 - Lab Page 6 of 8 5) Calculations for v O, vc, and ve:
ECE 311 - Lab Page 7 of 8 6) Calculated Ri - Calculated Ro - Calculations for Ri and Ro:
ECE 311 - Lab Page 8 of 8 7) Measured Ri - Measured Ro -