Performance Analysis of GaN Based Class D Amplifiers in Comparison to Conventional Si Based Amplifiers

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Addis Ababa University


Silicon has been the basis of semiconductor technology for the past couple of decades. Hence, engineers and manufacturers have made vast strides in silicon manufacturing, integrated circuit design, and semiconductor applications. However, due to the saturation of Moore's Law in recent years, Si-based semiconductor is about to see its limit in electronics applications. Meanwhile, there's a continuing need for faster, more efficient circuits. One of the paths forward from this point is for researchers and companies alike to look towards different materials to produce the devices of tomorrow. One material in particular that has caught the attention of the industry is gallium nitride (GaN). GaN power devices have lower specific on-resistance and faster switching speeds when compared to silicon power devices. These attributes make the GaN devices attractive for applications in the high efficiency class D audio amplifiers, a field that has not been widely studied. To that end, this thesis work set out to compare the performance of GaN based class D amplifiers with their Si counterparts. A class D audio amplifier was designed in the full bridge (bridge tied load – BTL) topology having a second order Butterworth filter for its output. The GaN based class D circuit had a high efficiency of about 97.7% while the Si had 85.7% at 100kHz switching frequency. It was also observed that as the switching frequency increased the efficiencies decreased. The GaN efficiency decreased to about 89.5% and the Si to 63.1% at 800kHz. This concludes that GaN class D amplifiers are certainly better than Si, especially for higher switching frequencies.