Gain-Bandwidth Trade-Off in the Cmos Cascode Amplifier

Abstract

The cascode ampli¯er has the potential of providing high gain and high bandwidth simultaneously. However, the design is not as intuitive as one might at¯rst think. In this paper, we present a detailed analysis of the single cascode ampli¯ers. The relationship between gain and bandwidth is important. When used to achieve maximum bandwidth the voltage gain of the common-source stage is close to unity. However, when the cascode is designed to obtain a high voltage gain, then the gain-bandwidth trade-o®, typical in the common source ampli¯er, reappears. This analysis is used to provide the basis for practical cascode ampli¯er design.