Aging in CMOS RF Linear Power Amplifiers: An Experimental Study

Abstract

An extensive experimental analysis of the hot carrier injection (HCI) and bias temperature instability (BTI) aging effects on RF linear power amplifiers (PAs) is presented in this article. Two different 2.45-GHz PA topologies have been implemented in a CMOS 65-nm technology: one based on a classical common-source (CS) and choke inductor and another one based on a complementary current-reuse (CR) circuit, both of them producing similar gain and output 1-dB compression point (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1dB</sub> ). These circuits have been stressed to produce accelerated aging degradation, by applying increasing supply (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD</sub> ) voltages or increasing RF input powers (PIN). The degradation on the transistor parameters (threshold voltage and mobility), dc bias point (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> current), and RF performance (gain, matching, and compression point) has been simultaneously measured. This has allowed us to observe how the reduced transistor degradation in CR PA results in higher robustness in its RF parameters compared with the CS PA circuit. The equivalent root-mean-square (rms) voltages have been proposed as an observable metric to assess the combined dc + RF stress in a PA circuit. This has been applied to a semianalytical model, providing comprehension of the link between the conditions under which a circuit is operated, the degradation of the transistor parameters, and the effects on the dc current and RF performance.