An offset-free LPF for /spl pi//4-shift QPSK signal generator

An intrinsically offset-free third-order active-RC LPF with 200 MHz cutoff is described. A /spl pi//4-shift QPSK signal generator for the personal handy phone system (PHS) was fabricated including the lowpass filters (LPF's) with a standard 0.6-/spl mu/m CMOS process, It operates from a 2.7 V power supply and dissipates 45 mW. The active die size is 2.0 mm/spl times/2.1 mm.