4902_C2009_Lab4

4902_C2009_Lab4 - EE4902 C2009 Lab 4 MOSFET Common Source...

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1 EE4902 C2009 Lab 4 MOSFET Common Source Amplifier with Resistive Load PURPOSE: The primary purpose of this lab is to measure the performance of the common source amplifier with a resistive load. The performance is measured in two ways: large signal and small signal. First, you will plot an input-output characteristic on the oscilloscope: input voltage on the X-axis and output on the Y-axis, as shown in Fig. 4-1. This plot shows the large signal behavior of the amplifier, with the MOSFET in all three regions: cutoff, saturation, and triode. The cutoff and triode regions set limits on the output swing at or near the power supply voltage rails. In the saturation region, the output characteristic shows a quadratic shape due to the square-law I D -V GS behavior of the MOSFET in the saturation region. VDD = +5V CD4007 VGS + - I D RD VDD + - VDD CUTOFF ACTIVE TRIODE V IN- V OUT =V tn V IN V OUT Fig. 4-1 V in = V TH V DS = V GS - V TH V out = V in - V TH V in V out
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2 To make this circuit function as a linear amplifier, we need to restrict the input signal amplitude so we use only a small portion of the characteristic in the saturation region, as shown in Fig. 4-2. VDD LINEAR APPROXIMATION Fig. 4-2. By using only a small portion of the quadratic, there is negligible deviation from a linear approximation, and the amplifier functions as a linear (almost) system.
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This note was uploaded on 10/13/2009 for the course ECE 4902 taught by Professor Mcneill during the Spring '01 term at WPI.

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4902_C2009_Lab4 - EE4902 C2009 Lab 4 MOSFET Common Source...

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