Dynamic range analog to digital converter suitable for hearing aid applications
An improved analog-to-digital converter device suitable for use in digital hearing aids, and methods for operating such a device are disclosed. Aspects of the present invention may provide a full 16–18 bits (96–108 dB) of dynamic range in a digital hearing aid circuit using 14-bit analog-to-digital converters typically available for hearing aid use. An embodiment of the present invention may use two analog-to-digital converters that are clocked by the same sampling trigger. One of the converters may be preceded by an amplifier having, for example, 24 dB of gain, while the other converter may be preceded by an amplifier having 0 dB of gain. The output of the first converter or the output of the second converter may be used, or a combination of the two outputs may be used to produce audio for the hearing aid user, depending upon input signal level.
1. A digital hearing aid comprising:
a first and second analog-to-digital converter, wherein the first analog-to-digital converter is a low-amplitude analog-to-digital converter, and the second analog-to-digital converter is a high-amplitude analog-to-digital convert; and
a digital signal processor that uses a first bit string from the first analog-to-digital converter when an input is below an amplitude level, and a second bit string from the second analog-to-digital converter when the input is above an amplitude level.
2. The digital hearing aid of claim 1 comprising a single amplitude level.
3. A digital hearing aid comprising:
a first analog-to-digital converter;
a second analog-to-digital converter; and
a digital signal processor that uses a first bit string from the first analog-to-digital converter when an input is below an amplitude level, and a second bit string from the second analog-to-digital converter when the input is above an amplitude level, wherein the digital signal processor uses the first bit string from the first analog-to-digital converter where the input is below a first amplitude level, the second bit string from the second analog-to-digital converter when the input is above a second amplitude level, and a combination of the first and second bit strings when the input is between the first and second amplitude levels.
4. A method of operating a digital hearing aid, the method comprising:
receiving a bit string from a first analog-to-digital converter, said first analog-to-digital converter being a low-amplitude analog-to-digital converter;
receiving a bit string from a second analog-to-digital converter, said second analog-to-digital converter being a high-amplitude analog-to-digital converter; and
processing the bit string from the first analog-to-digital converter when an input is below an amplitude level, and the second bit string from the second analog-to-digital converter when the input is above an amplitude level.
5. The method of claim 4 wherein the amplitude level is a single amplitude level.
6. A method of operating a digital hearing aid, the method comprising:
receiving a bit string from a first analog-to-digital converter;
receiving a bit string from a second analog-to-digital converter; and
processing the first bit string from the first analog-to-digital converter when the input is below a first amplitude level, processing the second bit string from the second analog-to-digital converter when the input is above a second amplitude level, and processing a combination of the first and second bit strings when the input is between the first and second amplitude levels.