Title :
An ultra-low-power, low-voltage electronic audio delay line for use in hearing aids
Author :
van Dijk, L.P.L. ; van der Woerd, A.C. ; Mulder, J. ; van Roermund, A.H.M.
Author_Institution :
Dept. of Electr. Eng., Delft Univ. of Technol., Netherlands
fDate :
2/1/1998 12:00:00 AM
Abstract :
In this paper, the design of an electronic audio delay line, realized with a second-order all-pass filter, is presented. The designed filter is primarily intended for use in hearing aids, to provide directivity by a specially designed microphone array. The filter operates at a supply voltage of as low as 1.8 V. The simulated and measured total quiescent current is 0.9 μA. Owing to current companding and class-AB operation, the dynamic range is 62 dB at a total harmonic distortion (THD) below 7%, i.e., at maximum output. The delay time is adjustable by control currents. The filter has been integrated in a standard bipolar process. The total measured delay time of the all-pass filter is approximately 110 μs over a bandwidth of 4 kHz
Keywords :
active filters; all-pass filters; compandors; delay lines; harmonic distortion; hearing aids; microphones; 0.9 muA; 1.8 V; 110 mus; 4 kHz; class-AB operation; control currents; current companding; delay time; directivity; dynamic range; electronic audio delay line; hearing aids; microphone array; second-order all-pass filter; total harmonic distortion; total quiescent current; Current measurement; Delay effects; Delay lines; Distortion measurement; Dynamic range; Filters; Hearing aids; Low voltage; Microphone arrays; Total harmonic distortion;
Journal_Title :
Solid-State Circuits, IEEE Journal of
