Design and Implementation of CMOS Power Amplifier for GSM Applications

The objective of this work is to design and implement a CMOS power amplifier for GSM Applications. Recent study shows that more analog blocks are being integrated onto single silicon CMOS Chip. The power amplifier becomes the final block in the transmit path and has to amplify the signal to required power level. Power amplifiers are extensively used in cell phones, base stations, cordless phones, WLAN etc. Class-C has become more useful where efficiency is a prime concern. A differential topology method is presented to design Power Amplifier (PA) for GSM applications. The differential topology suppresses the even higher harmonics at the output. The CMOS Class-C PA is suitable for applications which use constant-envelope modulation scheme where information is contained in phase e.g. BPSK and GMSK. This is an advantage for Class-C PA despite non-linearity of the output signal. The balun implemented in this design is not only used to link the differential PA to the single-ended load but also works as a output matching network. In this work the transistor size i.e. ‘W/L Ratio’, L and C values are set in order to maximize the Power Added Efficiency (PAE).