Question

4. In the diode circuit below diodes Day and Da2 are identical have a voltage of 0.7V at ImA current. The diodes Dbị and Db2 are identical and have 10 times the junction area of Dal. Also all diodes have n=2 and VI = 25mV. The circuit employs a supply current ISUPPLY=20mA. (a) Draw the i-v curve for diodes Da and D. Label axes and all relevant points. [8] (b) Find the value of Vout at nominal supply and no load. [20] Clearly mark the operating points of the diodes on the i-v curves. (C) If all diodes were made of type Da, would the output increase, decrease or stay the same? Explain your answer without doing any calculation. [10] (d) Why are a stack of diodes being used to provide Vout? [6] (e) Which diode is the better diode to use for the stack. Explain your answer. [6] Vsupply = 10V ISUPPLY Figure 4 + VOUT Dai D2 Doi D.2

Answer 1

For Dioda Da. A - 200 A ♡ I supply Vour. Dar Daz t IMA 0.8445 Dez IRI=0.8315 1 VE For Diode Dar NBE = 0.2V when I a = 1M A UBE NUT 0.txto 2 x 25 Ia = Inile IMA = Iar al To = 0.83150 Given Du have to time in to time in area than Da So IRI IR2 10 IR2 = 10 Те, 1 122 = 8.315 na 1 7 - Ia How for I supply = 20mA 20mA = IRI + ce 2x25 Similarly 0.8497V. For Diode Da @ 20mA. for Diode Do = 0.73465 V for Ia =20mA. Plot is on top of page. So on