ECE 3050 Analog Electronics Quiz 8October 14, 2009Professor Leach Nam eInstructions. Print y o ur n am e in the space abo ve. Place a box ar oun d your answers.Poin ts w ill be sub tracted if y o u do not expr ess each n u m erical answer a s a decim al numberand if you do not put a box around answers. Honor Code Statement: I have n eith ergiven nor received help on this quiz. In itials1. (a) Draw the circuit diagram of an npn Wilson curren t mirror and explain its principleadvan tage over the other curren t mirrors. — The circuit diagram is in the class notes.The advan tage is that it has a higher outp ut resistance and , therefore, looks mo re likean ideal curr ent source.(b) In typical application s, why must a two resistor v oltage divider be connected be-t ween a signal source and the input terminal to a transconductance op amp? — Theinput diff amp overloads at about 50 mV. When applying signals greater than thisvalue, the input must be attenuated with a v oltag e divider.(c) How is the gain of the transconductance op amp, i.e. current output divided byv oltage input, varied in a circuit? — By varying the current IABC.(d)Drawanopampcircuitthatcanbeusedtoconvertthecurrentoutputofthetranscond uctan ce op amp into a v olta ge while presen tin g a virtua l ground load on thetranscond uctance op amp. Giv e the equation for the v oltage output of the circuit as afunction of the current output of the transcond uctance op amp. — Th is is in the classnotes.2. (a) Assume all current mirrors are perfect and neglect the Early effect. Adjacen t to allunlabeled curren t arrows, label the current in term s of ic1and solv e for io(sc)in termsof ic1. — This is in the class notes. In addition, the notes give the dc currents in termsof IABC. It w as optional on the quiz to include them because they cancel at io(sc).(b) If the E arly effect is neglected, what is io(sc)in terms of vi1and vi2?io(sc)=vi1− vi22reor=gm2(vi1− vi2)
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