Page 274 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c05
260 MECHATRONICS Printer: Yet to Come October 28, 2014 11:15 254mm×178mm
For the second case the measured voltage is
( )( )
R L R in
v out = K amp s (5.88)
v
R + R out R + R s
in
L
( 100 )( 1 000 000 )
= ⋅ 1 ⋅ v s (5.89)
100 + 1 1 000 000 + 100
( 100 )( 1 000 000 )
= ⋅ v s (5.90)
101 1 000 100
= 0.990 ⋅ v (5.91)
s
= 9.90 V (5.92)
which shows an error of 1% of the correct value of the voltage. Notice that there are two
components to the error in the gain due to input and output loading, one due to the input
loading (K ) and and the other due to the output loading (K ),
1
2
v out = K ⋅ K ⋅ K amp s (5.93)
v
2
1
where,
( )
R in
K = (5.94)
1
R + R s
in
1 000 000
= (5.95)
1 000 100
( )
R L
K = (5.96)
2
R + R out
L
100
= (5.97)
101
This example illustrates that in order to minimize the effect of loading errors, components
should have very large input impedance (ideally infinite), and very small output impendace
(ideally zero).
5.5 SEMICONDUCTOR ELECTRONIC DEVICES
Electronic systems include components made using semiconductor materials, such as
diodes, SCRs, transistors, and integrated circuits (ICs). Pictures of some common semicon-
ductor devices are shown in Figure 5.9. Because current flow is accomplished through the
flow of electrons in the solid crystal structure of semiconductor materials, components made
from semiconductor materials are also called solid-state devices. The difference between an
electrical and electronic system lies in whether solid-state components (diodes, transistors,
ICs) are used in the circuit or not.

5.5.1 Semiconductor Materials

Semiconductor materials are the group IV elements in the periodic table. The most com-
monly used semiconductor materials are silicon (Si) and germanium (Ge). Semiconductor
materials have an electrical conductivity property that is somewhere in between the conduc-
tors and insulators (non-conductors), hence the name semiconductors. A silicon atom has
14 electrons, and four of these electrons revolve in the outermost orbit around the nucleus
(Figure 5.10a). In its pure form, silicon is not much use as a semiconductor. The crystalline