Bipolar-MOS and Bipolar IC's Building Blocks for Smoke-Detector Circuits

Some basic IC building blocks that effectively interface with ionization detectors and perform the additional functions of low-level battery indication and alarm activation are described. Also shown is how the recent advent of IC's using the combined bipolar and MOS technologies results in device characteristics that effectively interface with high-impedance sensors such as ionization chambers. Interface schemes such as the single-chamber with series resistor, series-connected dual chamber, and parallel-chamber connection are described in detail.