An airbag system comprises an airbag, an inflator, a squib, a high-side switch, a low-side switch, a firing circuit for switching the two switches, a first motion detecting circuit including an acceleration sensor, a second motion detecting circuit including an acceleration sensor, a first collision determining circuit for outputting a firing signal to the firing circuit, and a second collision determining circuit for outputting a firing signal to the firing circuit. The first collision determining circuit comprises an analog comparator for comparing a signal from the first motion detecting circuit with a reference value.