4902_C2009_Lab5

4902_C2009_Lab5 - 1 EE4902 C2009 - Lab 5 MOSFET Common...

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Unformatted text preview: 1 EE4902 C2009 - Lab 5 MOSFET Common Source Amplifier with Active Load Bandwidth of MOSFET Common Source Amplifier: Resistive Load / Active Load PURPOSE: The primary purpose of this lab is to measure the performance of the common source amplifier with active (current source) load. Additionally, you will measure the bandwidth of the common source amplifier with both active (current source) and passive (resistor) loads. The common source amplifier is an important topology to be familiar with for high gain applications - in single-ended signal situations, the common-source amplifier offers high gain and high input resistance. It will also be relevant in differential signal situations - when the differential amplifier is analyzed with half-circuit techniques, the result of the symmetry split is two common-source amplifiers. Upon completion of this lab you should be able to: Recognize the increased gain available with active loads, and the associated difficulty (and importance) of setting the correct input DC bias level when using high gain circuits. Recognize the gain-bandwidth tradeoff Using sine wave inputs, make detailed measurement of magnitude and phase response to construct a Bode plot Using a small square wave input, use the BW x t R = 0.35 relationship to quickly measure the bandwidth BW (f 3dB ) NOTE: This lab involves construction and measurement of circuits with high gains ( 100). It is extremely important to use bypass capacitors on the supply rail(s) to keep the power supply voltages clean. 2 LAB PROCEDURE 13 14 6 12 11 10 RB M2 (U2) M3 (U2) I B VDD = +5V I D Vout 5 4 3 M1 (U1) MC14007 7 7 + VTEST Fig. P2-1 SIGNAL SOURCE + Vin Figure L5-1. Vin +- FUNCTION 2 LAB PROCEDURE 13 14 6 12 11 10 RB M2 (U2) M3 (U2) I B VDD = +5V I D Vout 5 4 3 M1 (U1) MC14007 7 7 + VTEST Fig. P2-1 SIGNAL SOURCE + Vin Figure L5-1. Vin +- FUNCTION GENERATOR 3 MOSFET COMMON SOURCE AMPLIFIER WITH ACTIVE LOAD L5-1. Construct the circuit shown in Figure L5-1. In this case, the load is the current source formed by M2 and M3. Choose R B =100k for a DC drain current of I D 30A. Use the oscilloscope to monitor input and output voltage signals; also consider use of the DVM when more precise measurements are necessary. NOTE: the U1 and U2 designations in the schematics indicate that M2 and M3 are MOSFETs from a different physical package than M1. Although this isnt necessary for this circuit, it does make it easier for substituting a resistive load later in the lab. DC BIAS LEVEL Note: Be sure to set the function generator output menu to Hi-Z mode so the voltage readings on the function generator are correct. L5-2. Set the DC bias level at the input by setting the function generator to produce a DC only output. Adjusting the DC level at the function generator output until you observe the correct DC bias level ( +2.5V, midway between the supply rails) at the output of the common source amplifier....
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4902_C2009_Lab5 - 1 EE4902 C2009 - Lab 5 MOSFET Common...

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