Patent ID: 6998597

Claim:
A circuit for determining the radiation power of radiation which is incident on a photodiode ( 2 ), wherein the circuit applies a voltage signal to the cathode ( 8 ) of a reverse-biased photodiode ( 2 ) and detects the photodiode voltage (U D ) which is dropped across the photodiode ( 2 ), the circuit comprising: the reverse-biased photodiode, a voltage modulator, a low-pass filter, and a control unit; wherein an output ( 4 ) of the voltage modulator ( 37 ) is connected via the low-pass filter ( 5 ) to the cathode ( 8 ) of the photodiode ( 2 ), and the control unit ( 31 , 33 ) controls the voltage modulator ( 37 ) as a function of the photodiode voltage (U D ) with the aid of a manipulated variable ( 35 , 36 ) used for determining the radiation power.