University of California College of Engineering Department of Electrical Engineering and Computer Sciences Ben Wild Summer 2002 EE40 Problem Set 4 Due July 12 12pm Problem 1 short 1k 6k 5V VX 2k 12k k Find VX Hint DO NOT use nodal analysis that is too much work The only other tricks you know so far are series and parallel resistor formulas and voltage and current dividers Problem 2 medium 2mA 3k 2k 5k 5k 3V 3k 6k 3mA 5k a Identify a convenient place to put the ground node Beware if you select the wrong place to put the ground node you will create a floating voltage source b Label the unknown voltage nodes excluding the ground node c Write nodal equations at each node DO NOT simplify your equations Problem 3 medium 2V 1 5k 1 8V B C 5k Ix 0 4k 2 25k a Find Ix without performing Nodal Analysis EASY b Define a reference node to avoid floating voltage sources and use nodal analysis to find the voltage difference VC VB and the current from C to B through the 5K resistor Problem 4 medium 2k 0 2k 2mA 1k 0 4k 100 a Identify a convenient place to put the ground node b Label the unknown voltage nodes excluding the ground node c Write nodal equations at each node DO NOT simplify your equations Problem 5 short VX B A 2k 3k 0 5mA 0 3mA 3V 8k 4V IX 5k C Look this circuit over very carefully before beginning The effort depends quite a lot on how you proceed After that warning only a fool would start writing nodal equations Hint You will apply KCL and KVL judiciously And remember no current flows into or out of ground it is on the circuit diagram just to indicate the reference for potential a b c d Find VC Find IX Find VB Warning the voltage across a current source is rarely zero What is VX vB Problem 6 medium 6k 4k 3V 6V vA 0 75mA 4k Use Nodal Analysis to find VA and VB Yes numerical values please Problem 7 short A B C 3V 3k 2mA 5k D 2V 3k 6k A B C and D all have unknown node voltages Use nodal analysis to find 4 equations sufficient to solve for VA VB VC and VD DO NOT solve your equations Problem 8 medium Review of Pulse Distortion A 2V pulse of duration10nsec drives one of the signal nodes at the output of your microprocessor It drives this node call it node X through a resistance RX The capacitance of node X to ground is 1pF Assume that the voltage at node X much reach a minimum of 1 2 V to be correctly interpreted as a logic 1 a What is the maximum value of the resistance RX b At this value of RX what is VX 10nsec after the input pulse is finished that is 20nsec after the start of the pulse
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