The AD674B and AD774B are complete 12-bit successiveapproximation analog-to-digital converters with three-state output buffer circuitry for direct interface to 8- and 16-bit microprocessor busses. A high-precision voltage reference and clock are included on chip， and the circuit requires only power supplies and control signals for operation. The AD674B and AD774B are pin-compatible with the industry standard AD574A， but offer faster conversion time and busaccess speed than the AD574A and lower power consumption. The AD674B converts in 15 μs （maximum） and the AD774B converts in 8 μs （maximum）。 The monolithic design is implemented using Analog Devices’ BiMOS II process allowing high-performance bipolar analog circuitry to be combined on the same die with digital CMOS logic. Offset， linearity， and scaling errors are minimized by active laser trimming of thin-film resistors. Five different grades are available. The J and K grades are specified for operation over the 0°C to 70°C temperature range. The A and B grades are specified from –40°C to +85°C， the T grade is specified from –55°C to +125°C. The J and K grades are available in a 28-lead plastic DIP or 28-lead SOIC. All other grades are available in a 28-lead hermetically sealed ceramic DIP.