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Unformatted text preview: Experiment 7: Frequency Response 1 Objective You have already seen the performance of several BJT amplifiers. Even though they were each designed to operate well at certain small-signal frequencies, there is a frequency limit imposed on each of them by the innate parasitic capacitances of the BJTs. In this lab, you will observe how an amplifier responds to different frequencies as well as the effects of external capacitative loads and innate parasitic capacitances. 2 Materials The items listed in table 1 will be needed. Note: Be sure to answer the questions on the report as you proceed through this lab. The report questions are labeled according to the sections in the experiment. CAUTION: FOR THIS EXPERIMENT, THE TRANSISTORS CAN BECOME EXTREMELY HOT!!! Component Quantity 2N4401 NPN BJT 1 10 k resistor 1 1 k resistor 1 51 resistor 1 1 nF Capacitor 1 Table 1: Components used in this lab 3 Procedure The two following subsections are instructions on how to use the oscilloscope to make Bode magnitude and phase measurements. Please use them as references. 3.1 Technique for Measuring Magnitude using the Oscilloscope The following instructions assume you have an amplifier already built and that it has one input, v in , and one output, v out . In addition, the input, v in , must be controlled by the function generator. 1. Use the function generator to create a sine wave with the frequency of your choice; this shall be the v in for your circuit. 2. Also connect v in and v out to their respective channels on the oscilloscope. The following steps will assume that v in is on Channel 2 and v out is on Channel 1. 3. Press the Quick Measure button in the MEASURE section. Next, select Channel 1 as the source and Peak- Peak as the measurement. Now, press the third menu button that corresponds to Measure. 4. Repeat the previous step for Channel 2. 5. At the bottom of the screen, each peak-to-peak voltage will be displayed. Calculate Pk- Pk (1) Pk- Pk (2) ; this value should be the magnitude of the frequency response at the chosen frequency....
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- Spring '08