A Study of Operating Condition and Design Methods to Achieve the Upper Limit of Power Gain in Amplifiers at Near- f_{max}fmax Frequencies

摘要

A study of operating condition and design methods is presented that enables the amplifiers to achieve the upper limit of their power gain at frequencies close to the device f_{max}fmax . Using the gain-plane approach, the necessary and sufficient conditions to achieve this theoretical upper limit are obtained and the results are analytically verified. As will be demonstrated, the maximum power gain is achieved if and only if the imaginary part of Y_{12}/Y_{21}Y12/Y21 becomes zero and the device operates at the edge of the unconditional stability region. In addition, a generic circuit solution comprising both a YY - and a ZZ -embedding network is proposed to achieve this upper limit. Simulations of a CMOS amplifier surrounded by an exemplary YZ-embedding network verify this study.