thank u all, in fact i am looking to increase the SFDR factor but at same time i dont want toch the OTA because i have designed with PMOS as input, so i dont aspect much from pmos transistors for increasing the unity gain frequency and phase margin, i am going to design bootstrapped switch which can be a good soluation, same the figure below, so what u think about my idea , also how to simulate the switch (this is main matter now) any one intrested the paper is uploded for u
regards