The pulse waveform is one which abruptly makes a transition from its baseline to a new level of voltage or current, stays at that level for a brief time, then returns to its original baseline voltage. 2. Parameters of Pulse Waveform ReturnNext 9.1 Introduction 1. There are two methods to generate pulse waveform: (1) Generate by various multivibrator directly. (2) Transform a periodical waveform(Sine, Triangle, Sawtooth, etc.) to pulse waveform by transform circuits.

9.1 Introduction NextBackReturn The baseline would simply be the lowest (or most negative) value of the pulse train (series of pulses). There is usually an accompanying graph which shows the baseline level.

9.1 Introduction NextBackReturn Ideal Pulse — An ideal pulse makes an instantaneous transition from its baseline value to its new value and holds that exact value for a moment then instantaneously returns to its baseline valu e. A positive ideal pulse is shown in (a) and a negative ideal pulse in shown in (b) above. Nonideal Pulse — The real world must settle for the nonideal pulse which does not (cannot) change its value of voltage and/or current instantly. All change in the practical world requires time. The figure above shows the nonideal pulse in (c) and (d). Pulse Period (T)— The interval between the two adjacent pulses. Pulse Frequency(F) — The number of pulses per second.

9.1 Introduction NextBackReturn Amplitude(V m ) — Height of the pulse from its baseline to its peak value. Pulse Width(T w ) — The time of the pulse remains in its altered state (value different from that of the baseline) from its 50% point on the leading edge to the 50% point on its trailing edge. Rise Time(T r ) — The time of the pulse is in transition starting from the 10% point (0.1) on the leading slope (positive going in this case) to the 90% (0.9) point on the leading slope (also called "edge"). 后沿，尾沿

9.1 Introduction NextBackReturn Fall Time(T f ) — Time required to return to the baseline starting at the 90% point and ending at the 10% point on the trailing slope (also called "negative edge"). Values of current and voltage cannot change instantly because of reactance. This means the circuit's series inductance prevents the current from changing instantly and the circuit's parallel capacitance prevents the voltage from changing instantly. Capacitance and inductance react to change by developing opposing voltages which reduce and slow the current and voltage changes thus retarding their transitions. 电抗

9.1 Introduction Duty Cycle(q) — The ratio of the pulse width (T w ) to the period (T) and is usually expressed as a percentage. q = (T w /T)  100% q=(1us / 10us)  100% = 10%. q=(9us / 10us)  100% = 90%. This means the pulse waveform is working 90% of the time. BackReturn