 This device scaling, along with the advanced process control available in today's technologies, has recently made it possible to reach a transition frequency (ft) of 170 GHz and a maximum oscillation frequency (fmax) of 240 GHz in a 90 nm CMOS process.The operation of the DA can perhaps be most easily understood when explained in terms of the traveling-wave tube amplifier (TWTA).The DA consists of a pair of transmission lines with characteristic impedances of Z0 independently connecting the inputs and outputs of several active devices.