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| Analog
and Digital Signal |
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(I) Analog signal :
A continuously varying signal (voltage or current) is called
an analog signal. For example, an alternating voltage varying
sinusoidally is an analog signal see the fig (a). If such
an analog signal is applied to the input of a transistor amplifier,
the output voltage will also vary sinusoidally. This is the
analog operation i.e. the output voltage can have an infinite
number of values. Due to many-valued output, the analog operation
is less reliable. |
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Fig
(a) |
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(II) Digital Signal :
A signal (voltage or current) that can have only two discrete
value is called a digital signal. For example, a square wave
is a digital signal see the fig(b). It is because this signal
has two values viz. +5 V and 0 V and no other value. These
values are labeled as High and Low. The High voltage is +5
V and the Low voltage is 0 V. |
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Fig
(b) |
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If proper digital signal is applied
to the input of a transistor, the transistor can be driven
between cut off and saturation. In other words, the transistor
will have two-state operation i.e. output is either low or
high. Since digital operation has only two states (i.e. ON
or OFF), it is far more reliable than many-valued analog
operation. It
is because with two-state operation, all the signal are easily
recognized as either low or high. |
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