An ultra-low-power ultra-low-voltage linearized low noise trans-conductance amplifier

Abstract

With the proliferation of portable wireless applications and wireless sensor networks, such as internet of things (IoT), wireless body area networks (WBANs), and Bluetooth low energy (BLE), ultra-low-power (ULP) frontends have attracted a lot of attention. To maximize the battery lifetime or to work with harvested energy, it is critical to minimize power consumption and operate under ultra-low-voltage (ULV) supply. The low noise amplifier (LNA) is the first active block in the RF front end, which needs to provide impedance matching and sufficient gain, while maintaining low noise and high linearity. All these requirements conflict with low power consumption and low voltage. As the CMOS process is scaled to nanoscale, an ultra-low voltage design is more favorable, and it is one of the methods to achieve low power consumption. However, an ultra-low voltage supply limits the voltage swing and degrades the linearity performance of the LNA. A traditional LNA, giving gain in the voltage mode, is not suitable for an ULV design. Alternatively, an LNA in current mode or also known as a low noise trans-conductance amplifier (LNTA), followed by a low impedance mixer, gives low voltage gain, converts voltage to current, and pushes the current to voltage conversion to the baseband. In this case, no voltage gain is needed until it is at the end of the baseband. Good linearity and low noise can be simultaneously satisfied especially when a passive mixer is involved. Recently, current reuse and trans-conductance (gm) boosting techniques are mostly used to get low power consumption. By combining both techniques, power can be reduced further. So a new current reuse 4-times-gm boosting LNTA is proposed. However, these techniques sacrifice linearity of the front end. Thus, a linearization technique should be adopted. Traditional linearization techniques either are unsuitable for low voltage application or have a power penalty. The major components of nonlinearity of LNAs come from gm nonlinearity and drain-source impedance. So a new linearization technique is also proposed, which cancels the second and third nonlinear term of MOSFETS’ intrinsic gm at the same time, while drain-source impedance nonlinearity is also taken into consideration by optimizing the loading impedance of the LNTA. The proposed LNTA is successfully integrated as part of a ULV ULP receiver for BLE, IoT and WSN applications. It achieves a high input second order intercept point (IIP2) of 44.5 dBm with 42 dB improvement and input third order intercept point (IIP3) of 16 dBm with 13 dB improvement, and it achieves 3.2 dB NF, while only consuming 230 uW power with a 0.5 V supply voltage.

Date of Award	2018
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology