The push for miniaturization and higher frequency operation of the MAAL-011111 is challenging the limits of two key antenna connectivity components for wireless systems: the power amplifier (PA) and the low noise amplifier (LNA). Efforts to make 5G a reality and the use of PAs and LNAs in VSAT terminals, microwave radio links, and phased array radar systems have contributed to this transition.

Requirements for these applications include lower noise (for LNAs) and higher energy efficiency (for PAs) and operation at higher frequencies up to and above 10 GHz. To meet these growing demands, LNA and PA manufacturers are switching from traditional all-silicon processes to gallium arsenide (GaAs) for LNA and gallium nitride (GaN) for PA.

This article will describe the role and requirements of LNAs and PAs and their key characteristics, then describe typical GaAs and GaN devices and what to keep in mind when designing with these devices.

Sensitive role of LNA

The role of the LNA is to take an extremely weak, uncertain signal from the antenna, usually on the order of microvolts or below -100 dBm, and amplify that signal to a more useful level, typically around 0.5 to 1 V ( figure 1). Specifically, 10 μV is -87 dBm in a 50 Ω system, and 100 μV is -67 dBm.

Such gains can be easily achieved with modern electronics, but when the LNA adds all kinds of noise to the weak input signal, the problem is far less simple. The amplification advantage of the LNA is completely lost in such noise.