General Engineering Terms
"A" "B" "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P" "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

### Periodic Waveform.

A waveform that undergoes a pattern of changes, returns to its original pattern, and then repeats the same pattern of changes. Examples are square waves, rectangular waves, and sawtooth waves, as seen in the diagram below.

 Periodic Wave Shapes Of course any recurring waveform is considered periodic if it continues to repeat itself over the same time interval. These are the most common waveforms, shown with an example period. Except for the sine wave, the duty cycle could be anything, turning the rectangular waveform into the trigger waveform [given the right duty cycle]. Even complex waveforms could be considered periodic, because the only requirement is that they repeat the same pattern over the same time interval [over and over]. A sine wave modulating a sine wave carrier would be considered periodic as long as no information was imparted onto the wave.
 A trigger pulse is shown above as one of the waveforms that could be periodic. Although it is possible for a trigger to reoccur at the same interval, it is also possible that a trigger pulse could be completely random. AM Modulated Sinewave

A trigger pulse could be used to indicate changes in time, as in 1 pulse per second [1pps] or some other external change to a monitoring circuit as in an interrupt signal. One pulse per minute [1PPM] is also common. Normally the change in level between low to high is the important characteristic, as the high level could be any duration [100mS is common]. Although it's very common for the 1PPS signal to be TTL, some device may reproduce differential signals.

#### Related Waveform Topics

Almost any oscillator circuit will generate a sine wave.

Square waves can be easily generated by over driving the transistor circuit, or just using a digital IC. Square waves have a 50 percent duty cycle, with 50% of the signal high and low. A rectangular waveform or Trigger pulse is about the same as a square wave but with duty cycles other than 50%. Trigger pulses have very high or very low duty cycles, while rectangular pulses have duty cycles that are just above or below 50 percent.

Op Amp Oscillators;
Sine Wave Generator
Cosine Wave Oscillator & Sinewave oscillator.
Triangle Wave Oscillator & Rectangular wave oscillator.
Rectangular wave Oscillator & Square wave oscillator.
Sawtooth Generator circuit.

Transistor Oscillator: Trapezoid Waveform Generator, BJT circuit.
The above schematic link resides on the companion site, providing a general over-view of circuit operation.

The frequency of the Periodic Waveform will depend on the passive components used in the Osc. circuit.