NMOS will be better in terms of gm and hence thermal noise and bandwidth ( bandwidth will be larger at the cost of a worse phase margin ). PMOS will be better in terms of flicker noise ( however this might not be true depending on ur technology )
Thank you for your input. Your comments on gm and thermal noise make sense, but could you elaborate a bit on the BW / Phase margin tradeoff of using NMOS versus PMOS? What is the reason?
GBW = gm/C . So higher gm means higher gain bandwidth product for the same C
PM depends on the distance between the non-dominant pole and the unity gain frequency. So higher GBW will mean a smaller PM ( of course this is a very crude approx. The actual thinfg ill depend on ur circuit )
AND THE DFM consideration must been included,as the B and S terminal of NMOS can't been shorted in today's N-SUB processing,which can increase the factor of "base-gate"modulation.