Harmonic distortion test development for class-D amplifier
Williams, Kirt T
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Class-D amplifiers are quickly replacing Class-AB amplifiers in various audio applications because Class-D amplifiers are more efficient than Class-AB amplifiers. This is a very competitive market. The total harmonic distortion plus noise (THD+N) of an amplifier, along with its' efficiency, determines the quality of the amplifier. It has been determined that Class-D amplifiers are the most efficient of all the current Classes. The manufacturer's goal is to achieve the lowest possible THD+N on their Class-D amplifiers. However, all measurements including THD+N measurements can be time consuming and expensive. Manufacturing companies moved from bench testing to Automatic Test Equipment (ATE) testing as a solution to reduce test time. As ATEs became popular a variety has appeared with different configurations and price tags. Manufacturing cost accelerated because of the need for expensive ATEs. Manufacturing companies are trying to reduce test cost by moving various devices over to cheaper ATEs that produce equivalent (or almost equivalent within reason) results. For this project, a method for testing the THD+N for a Class-D amplifier will be created on four platforms (bench testing, LabVIEW testing, ATS-2 testing, and ATE testing). The resulting THD+N of the three platforms will be compared along with the THD+N measured on an ATE (Teradyne A567). The comparison shows how each platform varies in cost, ease of testing, and the level of THD+N measured.