Abstract
This paper presents a 50 MHz to 5 GHz broadband gain amplifier using a 0.5 μm gallium-arsenide pseudomorphic high-electron-mobility-transistor (GaAs pHEMT). For broadband design, a high gain cascode structure with a feedback network was used. To ensure the robustness of the design, the amplifier had to consider the effects of the Electrostatic Discharge (ESD)-protected diode and the package, which can degrade the broadband performance. Therefore, the equivalent circuit models of the package and the ESD-protected diode were analyzed and simulated in this paper. The designed broadband gain amplifier from 50 MHz to 5 GHz frequency band has a die size of 700 μm × 1000 μm and consumes 156 mW of dc power, and it was simulated with a gain of 18.7 dB to 20.6 dB, a P1dB of 15.3 to 16.9 dBm, and a OIP3 of 26.5 to 31 dBm. Furthermore, the excellent gain flatness exhibited within 18.7 dB ± 1.92 dB at the interest of the frequency band.
Highlights
The general broadband gain amplifier is widely used as the drive amplifier of a transmitter or a buffer amplifier in a receiver to provide a high linear dynamic range
We propose a broadband gain amplifier that includes the equivalent model of the package and Electrostatic Discharge (ESD)-protected diode to improve the robustness
The package and ESD protection diode models were considered because they operate as peripheral circuits that can change the impedance of the amplifier at high frequencies
Summary
The general broadband gain amplifier is widely used as the drive amplifier of a transmitter or a buffer amplifier in a receiver to provide a high linear dynamic range. A broadband gain amplifier using E-mode p-HEMT, which has similar Ft (unity current gain frequency) and low diffusion capacitance characteristics to InGaP HBT, has been reported [13] This p-HEMT process has an advantage in the general-purpose infra-structure industry for Sub-6 GHz because it has a precise process model and low production cost compared to the GaN process. The package and ESD protection diode models were considered because they operate as peripheral circuits that can change the impedance of the amplifier at high frequencies. The equivalent circuit model of the ESD-protected stacked diodes changes the impedance over high frequencies. It must be considered when designing a broadband amplifier. When the feedback method is used, the impedance varying range change is relatively small, so impedance matching is possible with a general matching network
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