0.07 mm2, 2 mW, 75 MHz-IF, fourth-order BPF using source-follower-based resonator in 90 nm CMOS

A highly-transistorised bandpass filter (BPF) using a source-follower-based (SFB) resonator is proposed. It benefits from the advantageous properties of the source follower (e.g. no parasitic pole, linear V_GS I/O relationship, high-input and low-output impedances), while combining it with a compact and low-power grounded differential active inductor to synthesise the complex poles. Fabricated in 90 nm CMOS, a fourth-order 75 MHz-IF BPF prototype merging two such SFB resonators measures a 10 MHz bandwidth at 2 mW of power. The die size is merely 0.07 mm².