A 100–170MHz fully-differential Sallen-Key 6th-order low-pass filter for wideband wireless communication

An integrated fully-differential 6th-order continuous time low-pass filter for wideband wireless communication is proposed in this paper. The filter is designed with the Sallen-Key biquadratic cells in which fully-differential operational amplifiers with two pairs of inputs are used. Stability optimization technology is discussed for the operational amplifier in order to improve its stability condition when it is closed loop to constitute unit gain Sallen-Key biquadratic cells. The filter is implemented in TSMC 0.13pm CMOS process, and has a core area of 0.5×0.22 mm2 excluding bonding pads. The simulated results show that the filter can operate successfully over a cutoff frequency range of 100MHz to 170MHz, and achieve more than 43dB adjacent channel rejection and more than 8.6dBm in-band IIP3. The power consumption is 15.5mA from a 1.2V supply voltage including 5mA of the output buffers.