Page 37 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

18 Chapter Three

Volts vPo5 volts Now consider a simple
VPOS
circuit consisting of a
resistor, a capacitor, and a
switch. Initially the switch
is in the OPEN (OFF)

position, the capacitor
voltage vCAP is 0 volts,
and no current is flowing
(Figure 3 -9).

CAP When the switch is
L
CLO5ED (turned ON),
any difference in potential
0
Volts
between vpos and VCAP
(b) At time To
(a) 5witch is open will cause current to flow
switch is closed
through the resistor. As
Figure 3-9. Resistor-capacitor-switch circuit usual, the direction of
current flow is illustrated
in the classical rather than the actual sense. The current flowing through
the resistor causes the capacitor to charge towards Vvos. But as the capacitor
charges, the difference in voltage between VYos and VCAP decreases, and conse-
quently so does the current (Figure 3-10).
I
VCA'i

Jpo5 Volt5

-63%

0 Volts

(a) Voltage characteristic of VCAP (b) Current flowing in the circuit

Figure 3-1 0. Voltage and current characteristics of resistor-capacitor-switch circuit