A high gain-flatness C-band variable gain LNA in a 0.25 μm GaAs pHEMT process

This paper presents a C -band (4-8 GHz) transconductance-controlled variable gain low noise amplifier (Gm- VGLNA) with excellent gain -flatness. The impedance and gain of the improved amplifier -cell (IA) are analyzed, and a current -controlled E -mode pHEMT load (CEL) structure is proposed to improve the gain -flatness performance in a wideband frequency range. The Gm-VGLNA is designed and fabricated using a 0.25 mu m GaAs pHEMT process. The measured results demonstrate a gain range of 11.5 dB, a return loss better than -8.3 dB over the operating frequency range, and a minimum noise figure of 2 dB. The best gain -flatness achieved is +/- 0.22 dB while the small signal gain is 15.2 dB, with gain -flatness better than +/- 0.78 dB over the entire operating gain range.