The design of a CMOS IF bandpass amplifier with low sensitivity to process and temperature variations

A fully differential CMOS IF bandpass amplifier (BPA) operated at 10.7 MHz is designed in 0.25 μm 1P5M CMOS process technology. In this design, the core of the bandpass filter is realized by a simple fully differential inverter with feedback NMOS source follower as the transresistance (Rm) amplifier. The load of the amplifier is the PMOS current source in parallel with the cross-coupled PMOS devices which generate the negative resistance for filter Q enhancement. The capacitors in series with the inputs of Rm amplifier is used to realize the Rm-C filter function. The BPA can be used to select an IF channel of 500 KHz. The filter IIP3 is -3 dB, whereas the gain at the center frequency is 37.4 db. The power dissipation is 6 mW at 2.5 V power supply. From the simulation results using the four-corner device model parameters (FF, FS, SF, SS), it is seen that the gain variation and the center frequency variation are 4.2 db and 470 kHz, respectively. In the temperature range of 0~80°C, the gain and center frequency variations are 4.1 db and 200 kHz, respectively; When the resistors vary ±10%, the gain and center frequency variations are 5.6 db and 900 kHz, respectively