PHYS 228 Final, Fall 2007

-Dt ^ zz-y / ^1 s F,E, JO^ OF Na me-', -Z-D : B ? (-f r Con h,) C tt< l. 2, 3. ,l f,, ( t V0 -l IIIIt II II IJ CL A b ] con\rol I '|+' KN Conko\ LD C \.K A 3 lp l/. Physi cs 228 - Final Exam January 2008 1. The circuit is used as an ohmmeter in a DMM. The DVM is 199.9 mV full-scale meter. What should the value of R. be so that the reading of the meter is in k0 directly? How large can the input bias current be so that the reading error in & is no more than l%? (20) 2. Find V.lVi as a function of frequency (20). 3. The comparator in the circuit controls the switch such that the switch is open when the comparator output is low and closed when the out put is high. Vo is periodic. Sketch Vo as a function of time. What is the frequency of the output? (20) 4. Find the power delivered by the source. (20) 5. What is the peak voltage across the resistor? (10) 6. The input to the circuit is two 4-bitnumbers. What is the function of this circuit? (10) 7. Construct the truth table for the circuit. Also, use Boolean algebra to write a simplified expression for the output in terms of A and B. (20) 8. Draw the time sequence of A and B, synchronized with the clock for Control : HI and Control : LO . Assume that A and B are LO initially. (20) 9. What is the power delivered by each source? (20) 10. Whatare the two functions (we considered in this course) that can be implemented with a 555 timer? What external elements do you need to implement each? (10) I 1. a) What is a Schmitt trigger? b) What is the characteristic impedance of a transmission line? c) What is the supe{position principle? (15) lD !< d. t. 2 loo Kt^s 5, 6,, Ao Bo Ar B, -1 soHT] _) A, -\\ R.4L Aa -) 3{ ouT