A wireless volume control receiver for hearing aids

The design of a practical wireless volume-control receiver for hearing aids is proposed in this paper. A trade-off design approach is introduced to solve the problem of minimizing the size of the receiver, reduce its power consumption, and maximize its performance. The receiver decodes standard dual-tone multifrequency (DTMF) signals and it requires only one multiplexed switched capacitor bandpass filter. Another unique component is the OTA design in weak inversion with reduced power supply, high voltage gain, and micropower dissipation. Most of the signals are processed using digital logic which contributes to the simplicity and power efficiency of the design. The IC layout of the receiver measures 1918 μm×1109 μm and it was implemented in a 2 μm CMOS technology with a 0.5 V threshold voltage. Experimental results using discrete (commercial) components show that the receiver can detect each valid frequency within 0.41% of the nominal value. A modified version of the receiver may be used as a DTMF decoder. This approach has also been used to design a wireless programmable interface for hearing aids