LOW-VOLTAGE LOW-POWER CONTROLLABLE PREAMPLIFIER FOR ELECTRET MICROPHONES

A low-voltage low-power analog controllable preamplifier for electret microphones is presented. It has been designed for a single supply vol tage of 1.0 V, whereas its average power consumption amounts to some t ens of microwatts. A de current controls its gain directly into decibe ls. The design meets specifications (listed in Section I) concerning a ccuracy, bandwidth, noise properties, etc., suitable for most applicat ions in portable telephone equipment, portable transceivers, hearing a ids, etc. Much attention has been paid to the dynamic range of the inp ut signal, noise, and offset properties. The circuit has been realized in a semi-custom IC process. Simulation and measurement data of the m ost important properties are presented.