Low-cost Multistage Direct-Coupled Linear Power Amplifier for Characterization of Magnetic Cores at Mulitple Frequencies

Magnetic components such as inductors, transformers and integrated magnetics are important components in power electronic converters including grid-tied inverters, isolated DC-DC converters and high-frequency-link converters. The magnetic cores in such applications are excited by various frequency components. Hence a quantitative understanding of the magnetic behaviour of these cores at various frequencies is valuable to power electronics research and development. This paper reports a cost-effective, multistage, direct-coupled, linear power amplifier for characterization of magnetic cores of interest at various frequencies. Different stages of the proposed amplifier ensure high voltage gain, high current gain and closed-loop operation to eliminate offset and other such non-idealities. The components involved in the amplifier are of low cost, and the characterization method does not require any transformer. Transformerless operation and direct-coupled nature of the amplifier contribute to its wide operating frequency range. The linear amplifier is capable of operating over a frequency range from DC to 100 kHz. Measurement of B-H characteristics of a ferrite core using the developed amplifier is demonstrated at different frequencies.