The Design Of The Record/Playback IC For Speech

Nowadays, record/playback ICs become more useful, and have optimizing market prospects. For this reason, the study and design of this type of ICs has attracted much attention recently. And the record/playback 1C, using one-bit delta modulation (ADM), has been designed and made widely for its simple production and feasibility.In this paper, a record/playback 1C using ADM is designed systematically. The ADM algorithm is described and implemented with mixed-signal CMOS circuits. The ADM system mainly includes a oscillator, a clock generator, an amplifier, a pre-amplif ier, a comparator, an AGC(Automatic Gain Control), an ADM analyzer&synthesizer, a D/A converter and a lowpass filter. Many circuit design techniques are incorporated into the design of the proposed ADM system so that the range of input signal level can be enlarged and the number of transistors used can be reduced. To extent the use of this 1C, some circuit blocks are added.In the design, digital circuits are used to process the signal and control the precision of coding. And some circuits are used in different time by several functions to reduce the number of transistors used and the dissipation. The 2-stage differential transconductance amplifier is used in the design to achieve high gain. In the design of amplifier, a resisterand a Miller capacitor is used to deal with the stability and frequency compensation. And a AGC system and a ring oscillator are also used.The whole circuit is simulated at system level. It works properly, and verifies the ADM algorithm. Main performance parameters are lObits resolution in prediction coding and 16KS/S sampling rate. The chip can be used in consumer field.