Overcome Mismatched Load Impedance in Arbitrary Function Generators (.PDF Download)

Arbitrary function generators (AFGs) are used to generate many different types of electrical waveforms, such as sine waves, square waves, triangular waves, and arbitrary waveforms. In addition, most electrical engineers use an AFG as a reference source for their device under test (DUT). With a relative frequency range from dc to 250 MHz, the latest AFGs can cover the audio frequency band, the video frequency band, and the radio frequency band. In all cases, impedance matching is required to maximize power transfer and minimize signal reflection.

The AFG’s output impedance should be equal to the load impedance or characteristic impedance. For example, in audio systems, 60 Ω is used as the characteristic impedance; in video systems, 75 Ω is used as the characteristic impedance. For the radio frequency band, the most common characteristic impedance is 50 Ω, which is the compromise value between minimum loss and optimum power-handling capability.