A new current-mode synthesis method for dynamic translinear filters and its applications in hearing instruments
A new current mode synthesis method for dynamic translinear filters is proposed. As a design example, we have considered an ultra-low power second order filter working in audio frequency range, for hearing aids application, and using subthreshold MOS devices. It has a nominal supply voltage of 1.2 V and works down to 1 Volt. It has a power consumption of 5 mu W. The filter cut-off frequency and its Q factor can be tuned respectively from 600 Hz to 13 kHz and from 0.6 to 1.1. Mismatch problems are investigated on the circuit level and an on-chip compensation method is proposed.
dynamic translinear hearing instruments subthreshold mos low voltage low power filter design audiofrequency