Compact and Efficient Wideband Variable Gain LNA MMIC on InGaAs pHEMT

In this paper, the design of wide-band variable gain low noise amplifier (VGLNA) MMIC operating in 4-10 GHz frequency range has been presented. The MMIC has been designed and fabricated on 0.15um InGaAs pseudomorphic high electron-mobility transistor (pHEMPT) process from WIN Semiconductors Corporation. The proposed design consists of two amplifier stages: First stage is constant gain, low noise stage whereas the second stage is variable gain stage. In order to achieve flat gain in wide bandwidth, RC feedback topology is used in both the stages. The measured results show good agreement with the simulation results. The measured Gain of the VGLNA MMIC is 19 dB and the noise figure is 2.5 dB. Gain flatness of better than ±0.7 dB is achieved from 4 to 10 GHz, which corresponds to extremely wide flat gain bandwidth of 85%. The measured input and output return losses are better than 10 dB in the whole frequency band. The Gain is controllable by external DC control voltage. Gain variation range of more than 20 dB is achieved corresponding to control voltage variation from 0 to 3V. The maximum output power, corresponding to 1-dB compression point is +2 dBm. The chip consumes 60mA nominal DC current at +3V DC supply voltage; which corresponds to very low DC power consumption of 180mW. The VGLNA MMIC only utilizes two active p-HEMT devices and the occupied fabrication area is 1.5 mm x 0.8 mm; which is quite compact for this circuit. To our knowledge, these performance parameters are among the best reported up till now for variable gain LNA MMIC developed on GaAs pHEMT, in this frequency range.