Lpl. Vandijk et al., AN ULTRA-LOW-POWER, LOW-VOLTAGE ELECTRONIC AUDIO DELAY-LINE FOR USE IN HEARING-AIDS, IEEE journal of solid-state circuits, 33(2), 1998, pp. 291-294
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 su
pply voltage of as low as 1.8 V, The simulated and measured total quie
scent current is 0.9 mu A, Owing to current companding and class-AB op
eration, the dynamic range is 62 dB at a total harmonic distortion (TH
D) 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 appr
oximately 110 mu s over a bandwidth of 4 kHz.