Some Standard Signals

(a) sin Ï‰t   (b) cos Ï‰t

Sinusoidal Signal A sinusoid is a signal that has the form of a sine or cosine function.

We consider a sinusoidal voltage, v(t) = Vm sin Ï‰t

where
Vm is the amplitude,
Ï‰t is the argument of the sinusoid,
Ï‰ is the angular frequency of the sinusoid in rad/s = 2Ï€Ï† = ,
and T is the time period of the sinusoid.

Exponential Signal An exponential signal is a function of time defined as

f(t) = 0, t < 0

Keâ€“att â‰¥ 0

where K and a are some real constants. The reciprocal of a has the dimension of time and is known as time constant, . This is the time to reach 63.2% of the total change from the initial to final value.

Square Wave Signal A square wave is a type of waveform where the signal has only two levels. The signal switches between these levels at regular intervals and the switch is instant.
An ideal square wave signal is shown in the figure.

Square Wave Signal

Thus, square wave is a special kind of non-sinusoidal periodic signal with a time period T.
Square waves are universally encountered in digital switching circuits and are naturally generated by binary logic devices.