Download ETEE3211 Fall 2003

ETEE3211
Fall 2003
Test #1
Name:__________________
Show all work. Clearly indicate final answer(s).
1. (20 points) A particular diode has a reverse saturation current of 0.2µA, n=1.6, and
VT=26mV. Determine the diode current when the voltage across the diode is 0.4V. Also
determine the forward resistance of the diode at this operating point. Hint: Assume zero
contact resistance.
2. (40 points) Determine the capacitor size for
the circuit shown to the right when a=6 and
Rload=100Ω. The minimum voltage to the load
must not drop by more than 20%. Consider the
diodes and transformer ideal.
3. (40 points)
a. The input voltage to the clipper circuit in figure (a) varies linearly from 0 to 150V.
Sketch the output voltage, vout, on the same time plot as the input. Assume the diodes
are ideal.
b. Repeat part (a) for the circuit in figure (b).
EXTRA CREDIT (20 points max):
An integrated circuit requires plus
and minus voltages for their
operation. Using the circuit to the
right, determine the transformer
winding ratio and the capacitor size
needed to get a maximum of 14V
and a minimum of 12V at the
output when the input is 120Vrms
60Hz, VON=0.7V for each of the
diodes and Rf=0. Ignore transformer loss.
(HOPEFULLY!) USEFUL STUFF
T
vout , avg
Ri =
1
1
= ∫ vout (t ) dt =
T 0
T
Vs min − Vz
V
− Vz
= s max
I L max + I z min I L min + I z max
iD = I O (e
%reg =
vD
nVT
− 1)
V out max−Vout min
*100
Voutno min al
V
− VZ
C F = s max
∆Vf p Ri
T /2
∫
0
V
2πt
1
V0 sin
dt + ∫ 0 dt = 0 + 0 ≈ 0.318V0
π
T
T T /2
T
kT = -2.0 mV/oC for Si, –2.5 mV/oC for Ge
26mV@room temperature
rd =
nVT
iD
C=
Vmax
∆Vf p RL
VON (TNew ) − VON (Troom ) = kT (TNew − Troom )
I 0 ( atT2 ) = I 0 ( atT1 )e ki (T2 −T1 )
J = q ( pµ p + n µ n ) E
R=
ρL
A
=
L
σA
I z max =
IL min (Vz − Vs min ) + IL max (Vs max − Vz )
Vs min − 0.9Vz − 0.1Vs max