Function Generator

- key points about the function generator for understanding what is a function generator, what can it be used for, and how it works.

Function generators are items of test equipment that are able to generate a variety of simple repetitive waveforms. Straightforward signal generators such as RF signal generators or simple audio oscillators focus on producing a good sine waves, but in many cases other waveforms are needed.

In addition to producing sine waves, function generators may typically produce other repetitive waveforms including sawtooth and triangular waveforms, square waves, and pulses. Another feature included on many function generators is the ability to add a DC offset.

Often some of the low end function generators may only operate up to frequencies of possibly around 100 kHz as the various shaped waveforms are normally only needed at lower frequencies. However many other more comprehensive function generators are able to operate at much higher frequencies, often up to 10 or 20 MHz.

TTi TG2000 Function Generator

Function generator capabilities

Function generators are capable of producing a variety of repetitive waveforms, generally from the list below:

  • Sine wave:   A function generator will normally have the capability to produce a standard sine wave output. This is the standard waveform that oscillates between two levels with a standard sinusoidal shape.

    Sine wave from a function generator

  • Square wave:   A square wave is normally relatively easy for a function generator to produce. It consists of a signal moving directly between high and low levels.

    Square wave from a function generator

  • Pulse:   A pulse waveform is another type that can be produced by a function generator. It is effectively the same as a square wave, but with the mark space ratio very different to 1:1.

    Pulse wave from a function generator

  • Triangular wave:   This form of signal produced by the function generator linearly moves between a high and low point.

    Triangular wave from a function generator

  • Sawtooth wave:   Again, this is a triangular waveform, but with the rise edge of the waveform faster or slower than the fall, making a form of shape similar to a sawtooth.

    Sawtooth wave from a function generator

Function generator controls

In addition to a selection of the basic waveforms that are available, other controls on the function generator may include:

  • Frequency:   As would be expected, this control alters the basic frequency at which the waveform repeats. It is independent of the waveform type.
  • Waveform type :   This enables the different basic waveform types to be selected:

    1. Sine wave
    2. Square wave
    3. Triangular wave
  • DC offset:   This alters the average voltage of a signal relative to 0V or ground.
  • Duty cycle:   This control on the function generator changes the ratio of high voltage to low voltage time in a square wave signal, i.e. changing the waveform from a square wave with a 1:1 duty cycle to a pulse waveform, or a triangular waveform with equal rise and fall times to a sawtooth.

By Ian Poole

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