ECE 20 - Ex. 9

The George Washington University
School of Engineering and Applied Science
Department of Electrical and Computer Engineering
Summer 2000

Experiment # 9
Design of MOSFET Amplifiers and Current Mirrors

Equipment:
You must make up a complete equipment list and have your instructor review it before you start.

Objectives:

To find the best operating point for a MOSFET amplifier

To design a CSC amplifier according to a set of specifications

To design a CDC amplifier with current mirror according to a set of specifications

To establish the relationship between the voltage gain and the load

Figure # 1

1.- (HW) Design of Common Source

Design a Common Source voltage amplifier (with shorting capacitor) similar to the one shown in Fig # 1. Use ORCAD to verify that all the specifications have been achieved.

Design Specifications of the Amplifier

VDD = 24 V DC

|AV| > 20 (when loaded with RL= 1 k W )

RIN > 200 KW

vin max(before distortion) ³ 60 mVpeak (when loaded with RL=1 k W)

Maximum Power Transfer must occur when loaded with RL= 1 k W+ 5%

Show all design calculations.

Compare the SPICE results to your design calculations and specifications and explain any and all differences.

2.- Assembly, Test and Verification of Specifications

Build and test your design. Measure and verify that your design meets all the given specifications.

a.Measure VG, VS, VD, and ID with no input.

b.Measure Avo, Av(RL= 1K), Rin (input impedance) and Rout (output impedance) of the assembled circuit.

c.Find the maximum input voltage that the amplifier can accept before the output distorts.

d.Measure the phase relationship between the input and output voltages.

Figure # 2

3.- (HW) Design

Design a Common Drain voltage amplifier with current mirror similar to the one shown in Fig # 2. Use SPICE to verify that all the specifications have been achieved.

Design Specifications of the Amplifier

VDD = + 10 Volts DC

ID = 15 mA

|AV| = 1 (when loaded with RL= 1 k W )

RIN ³ 500 KW

ROUT £ 100 W

vout max (before distortion) ³ 4 Vpeak (loaded with RL=1kW)

Show all design calculations.

Compare the SPICE results to your design calculations and specifications and explain any and all differences.

4.- Assembly, Test and Verification of Specifications

Build and test your design. Measure and verify that your design meets all the given specifications.

a.Measure VG, VS, VD, and ID with no input.

b.Measure Avo, Av(RL= 1K), Rin (input impedance) and Rout (output impedance) of the assembled circuit.

c.Find the maximum input voltage that the amplifier can accept before the output distorts.

d.Measure the phase relationship between the input and output voltages.

5.- Analysis

a. Compare the measured results to your design calculations and specifications. Explain any and all differences.

b. Write equations and plot the AC and DC load line of Common Source and Common Drain. Explain how to pick a good point for CSC and CDC from the AC and DC load line.

c. Is the current source design of the CDC (Fig. 2) a better choice compared to the configuration given in Fig. 1? If so, why?