A novel technique for the on-chip tuning of monolithic filters

Monolithic analog filters, with the exception of switched capacitor filters need on-chip tuning. Existing schemes of PLL and master-slave techniques use phase control for tuning. The proposed method uses amplitude detection, where the reference voltage itself is derived from the input. Much work has recently been done on active RC continuous-time filters in VLSI [4]-[8]. The heart of all such systems is an integrator with a voltage-variable time-constant (VVI). To generate the control for the VVI, these schemes use either a self-tuning filter (follow the master technique) [5] or a phase-locked loop [8], locking on to a stable reference frequency. Unlike these techniques which are essentially phase-control schemes, what is proposed here is a gain-control scheme.