A function generator is a piece of electronic test equipment used to generate repetitive waveforms. These waveforms can then be injected into a device under test and analyzed as they progress through the device, confirming the proper operation of the device or pinpointing a fault in the device.
Function generators usually generate a triangle wave as their basic output by repeatedly charging and discharging a capacitor from a constant current source. This produces a linearly ascending or descending voltage ramp. As the output voltage reaches upper and lower limits, the charging and discharging is reversed, producing the linear triangle wave. By varying the current and the size of the capacitor, different frequencies may be obtained.
Function generators, like most signal generators, may also contain an attenuator, various means of modulating the output waveform, and often contain the ability to automatically and repetitively “sweep” the frequency of the output waveform between two operator-determined limits. This capability makes it very easy to evaluate the frequency response of a given electronic circuit.