Window comparator

摘要

The invention relates to a window comparator for checking the position of an input voltage with respect to two test voltages limiting a voltage range at the top and bottom. The input voltage is supplied to the part-voltage taps of two voltage dividers (R1, R2; R3, R4) connected in series with one another at a constant voltage (U+, U-) via in each case one forward-connected and one reverse-connected diode (D1, D2). The junction of the two voltage dividers is connected to one input of an operational amplifier (OP). The output voltage of the operational amplifier (UA) is supplied to a diode bridge circuit (D3...D6), in the direct-current branch of which the light-emitting diode path of an optocoupler (OK) is connected in series with a Z diode (Z). The phototransistor of the optocoupler is monitored for conduction. When the input voltage exceeds or drops below one of the voltages acting as test voltage at the part-voltage taps of the voltage dividers, this leads to the displacement of the input potential of the operational amplifier and thus to it being driven towards the positive or negative side. Both have the effect that the phototransistor of the optocoupler becomes conductive. <IMAGE>