A single-chip ADM LSI CODEC

This paper describes the circuit design of an ADM (adaptive delta modulation) LSI CODEC with filters. The LSI chip is mounted in a 16-pin DIP and can operate with single low voltage supply. In order to realize a low power dissipation LSI IC, switched capacitor technology was used in the design of input/output filters and integrators, and C-array D/A converters and low voltage analog circuits were developed. An operational amplifier with a complementary differential input stage and a comparator with a capacitor-coupled input stage were employed to obtain a wide input voltage range with a low voltage supply. This CODEC achieves speech quality higher than that of 6-bit μ-law PCM CODEC at 32 kbits/s and power dissipation of below 30 mW.