CIRCUIT APPARATUS FOR MEASURING LUMINOUS INTENSITY

In a circuit arrangement for carrying out light intensity measurements, comprising an input terminal (5), an output terminal (6), a first and a second photodiodes (D1, D2) for receiving light emitted by an optical light source (S) and a first and a second operational amplifiers (1, 2) for receiving output current signals of the first and second photodiodes (D1, D2) generated under influence of the emitted light, the novelty lies in further comprising a four branch bridge circuit including in two adjacent branches the first and second photodiodes (D1, D2) coupled to a common point by their respective poles of the same sign and oppositely to them in the further two adjacent branches two bridge resistors (R1, R2), a third operational amplifier (3) for supplying power to the optical light source (S), current generator means connected by its input to the input terminal (5) and by its one output to the common point and an input of the third operational amplifier (3) for driving the bridge circuit, wherein the first operational amplifier (1) is inserted between the first photodiode (D1) and the junction point of the bridge resistors (R1, R2), and the second operational amplifier (2) is connected by its input to the second photodiode (D2) and by its output led to the output terminal (6) is reversely connected to the input by means of a compensation resistor (Rk).