4902_C2009_Lab1

4902_C2009_Lab1 - EE4902 Lab 1 C2009 Determining...

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1 EE4902 Lab 1 C2009 Determining Capacitance with Risetime Measurement Reverse Biased Diode Junction Capacitance MOSFET Gate Capacitance Simulation: SPICE Parameter Extraction, Transient Analysis PURPOSE: The purpose of this lab is to measure the capacitance of a reverse biased PN junction, and the gate capacitance of the MOSFET. Since these capacitances are small (of the order pF) you will also see the measurement effects of stray capacitances due to the breadboard and scope probe. Upon completion of this lab you should be able to: Recognize the capacitive nature of a reverse biased PN junction Recognize that the gate of a MOSFET looks (mostly) capacitive, and determine the gate capacitance per unit area and gate oxide thickness for the CD4007 Use the rise time = 2.2 τ relationship to determine the RC time constant τ of a network from a rise time measurement on an oscilloscope. Use simulation to confirm your value of the gate oxide thickness parameter TOX. General lab tips: a) Keep physical layout neat and organized, similar (if possible) to circuit diagram topology to aid in troubleshooting. b) Keep leads short (especially on high-impedance nodes) to avoid noise pickup. Running the supplies and ground as shown on the following page simplifies connections on your breadboard. Use bypass capacitors (0.01 µ F or 0.1 µ F) between the supply rails and ground. See suggested breadboard configuration on following page! c) Measure power supply voltages at the breadboard socket before inserting ICs. Beware of excessive voltage or polarity reversal. d) Turn off power supplies before making circuit changes. e) Make sure that your oscilloscope is properly configured: use the calibration signal source on the oscilloscope to be sure the scope probe attenuation is correct (10X, not 1X) and the probe is properly compensated, etc. Double-check settings if you see an unexpected measurement result. This is one of the many good reasons to do the prelab : if know what to expect, you can catch mistakes early before wasting too much time in lab. f) Note that the scopes in AK227 can save screen shots to a memory stick using the front panel USB port . Feel free to use screen shots of the oscilloscope waveforms to illustrate your measurements as appropriate.
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2 GND GND Suggested breadboard configuration (example with op-amp circuit).
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4902_C2009_Lab1 - EE4902 Lab 1 C2009 Determining...

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