California State University Sacramento College of Engineering and Computer Science Department of Electrical and Electronic Engineering CPE 102 01 Analog Digital Electronics Spring 2007 Homework 2 Due Wednesday 3 7 07 Each problem is worth 2 points unless otherwise specified Show all work 1 A silicon diode has a characteristic reverse saturation current Is 2 3x10 14 A when it operates in an electronic chassis at an ambient temperature of 28 C Assume the nonideality factor for this diode is n 1 The diode is driven by an ideal current source at 2 5 mA as shown in the figure Find the following a The diode voltage VD b The expected change in diode voltage VD if the temperature decreases by 20 C and the diode current is maintained constant at 2 5 mA 2 4 pts Assume a silicon Zener diode at room temperature has the following characteristics a Junction crossectional area A 3x105 m2 b A reverse bias breakdown voltage VR 7 21 V and junction potential j 0 932 V c ni 1010 cm3 s 1 04x10 12 F cm and Emax 3x105 V cm for silicon at breakdown Find the following a The width of the diode depletion region at breakdown wd b The donor and acceptor doping concentrations ND and NA Let ND NA for this diode c The reverse bias junction capacitance of the diode at breakdown Cj d The forward bias diffusion capacitance CD of the diode if the diode transit time 11 ns and the diode current ID 3 5 ma 3 Given a silicon diode with Is 2 3x10 16 A operating at room temperature find the Qpoint VD ID for the diode in the following circuit where Vs 1 00 V and R 82 Determine the Q point current and voltage values to three significant figures using any two of the methods in the following hint Hint You should consider one of three ways to do this Graphical Load Line solution Transcendental Equation solution and PSpice solution 1 R Vs 4 a A Zener diode with a nominal breakdown voltage Bv of 7 volts demonstrates a Zener voltage of 7 483 V and a Zener current of 347 A when operating in its breakdown region Determine the diode s effective Zener resistance RZ b If this diode is placed in the following voltage regulation circuit determine the value of R necessary to have it operate with the Zener voltage and current in part a 5 3 pts Determine the Q points VD ID for each of the three diodes in the circuit shown below Note Assume 0 6 V for the voltage drop across a forward biased diode Take an educated guess at the on off condition of each diode analyze the circuit and check your assumptions R1 2 2 k R2 1 8 k R3 1 k R4 3 3 k 6 3 pts The half wave rectified power supply circuit shown in figure 3 61 b in your text is to be designed with the following specifications f 60 Hz vS rms 25 2 V R 9 2 and Vr 0 25 V Find vo C ISC IP PIV and PD Total You should assume Von 1 2 V and Rs 125 m here 7 Do Problem 3 131 b in your text 8 Do problem 3 144 in your text Assume a 0 75 voltage drop across the forward biased diode 3