Sigma-delta adc circuit with bias compensation and microphone circuit having a sigma-delta adc circuit with bias compensation

A sigma-delta analog-to-digital converter (ADC) circuit, the sigma-delta ADC circuit comprising:

• a pair of operational transconductance amplifiers (OTAs);
• a filter connected to the pair of OTAs;
• a quantizer connected to the filter;
• a differential digital-to-analog converter (DAC) connected to the quantizer, wherein an output of a single-ended microphone and a differential output of the differential DAC are inputted into a plurality of input terminals of the pair of OTAs;
• and
• a bias compensation circuit configured to measure a biasing condition of a first OTA of the pair of OTAs and to apply the biasing condition of the first OTA to a second OTA of the pair of OTAs to reduce Total Harmonic Distortion Plus Noise (THD+N) in the sigma-delta ADC circuit, wherein the first and second OTAs and the bias compensation circuit are connected to same bias voltages.

A microphone circuit, the microphone circuit comprising:

• a single-ended microphone;
• and
• a sigma-delta analog-to-digital converter (ADC) circuit connected to the microphone, the sigma-delta ADC circuit comprising:
• a pair of operational transconductance amplifiers (OTAs);
• a filter connected to the pair of OTAs;
• a quantizer connected to the filter;
• a differential digital-to-analog converter (DAC) connected to the quantizer, wherein an output of the single-ended microphone and a differential output of the differential DAC are inputted into a plurality of input terminals of the pair of OTAs;
• and
• a bias compensation circuit configured to measure a biasing condition of a first OTA of the pair of OTAs and to apply the biasing condition of the first OTA to a second OTA of the pair of OTAs to reduce Total Harmonic Distortion Plus Noise (THD+N) in the sigma-delta ADC circuit.