# Some Standard Signals

**(a) sin**

*Ï‰t*(b) cos*Ï‰t***A sinusoid is a signal that has the form of a sine or cosine function.**

*Sinusoidal Signal*We consider a sinusoidal voltage,

*v*(*t*) =*V*sin_{m}*Ï‰t*where

*V*is the amplitude,

_{m}*Ï‰*

*is the argument of the sinusoid,*

_{t}*Ï‰*

*is the angular frequency of the sinusoid in rad/s = 2*

*Ï€Ï†*= ,

and

*T*is the time period of the sinusoid.

**An exponential signal is a function of time defined as**

*Exponential Signal**f*(

*t*) = 0,

*t*< 0

*Ke*

^{â€“at},

*t*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.**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.**

*Square Wave Signal*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.