Page 47 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

28 rn ChapterFour

Semiconductor Diodes
As was noted above, pure crystalline silicon acts as an insulator. By
comparison, both P-type and N-type silicon are reasonably good conductors
(Figure 4-4).

+ve +ve
doesn’t oes oes
onduct onduct +ve and -ve indicate
positive and negative
voltage ~ources,
respectively (for
Pure P-type N-type example, they could be
silicon silicon 5i I icon wires connected to the
terminals of a battery)

-ve -ve -ve

Figure 4-4. Pure P-type and N-type silicon

When things start to become really interesting, however, is when a piece
of silicon is doped such that part is P-type and part is N-type (Figure 4-5).

The silicon with both
+ve +ve
does P-type and N-type material
Onduct conducts electricity in only
N-type P-type one direction; in the other
silicon silicon
direction it behaves like an
P-type N-type
silicon silicon OPEN (OFF) switch. These
structures, known as semi-
conductor come in
-ve 5emiconductor -ve many shapes and sizes; an
diode
example could be as shown
Figure 4-5. Mixing P-type and N-type silicon in Figure 4-6.
-+ The “semiconductor” portion of
Approximate actual size

semiconductor diode was initiallv
used to distinguish these compo-
(a) Diode component (b) 5ymbol nents from their vacuum tube-
based cousins. As semiconductors
took over, everyone started to just
Figure 4-6. Diode: Component and symbol refer to them as diodes.