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.