Detection circuit including a noise reducing module having a switch connected between a photodiode and an integrating circuit
View Patent ↗The detection circuit comprises a switch connected between a photodiode and an integrator. It further comprises means for alternately switching bias conditions of the photodiode between a reverse bias and another state. The electronic traps in the photodiode are regularly passivated during the other state.
1. Detection circuit comprising:
a switch,
a photodiode connected to a first main terminal of the switch,
an integrator connected to a second main terminal of the switch and arranged so as to receive the signal emitted by the photodiode,
an alternating switching circuit configured for reverse biasing the photodiode during a first period and for biasing the photodiode in an other state during a second period, wherein the switch is configured so as to be in a blocking state when the photodiode is in the other state.
2. Circuit according to claim 1 , comprising a readout circuit including the integrator, the readout circuit being configured so as to apply a bias voltage to one of the terminals of the photodiode via the switch and wherein the alternating switching circuit is configured for applying a voltage to a control electrode of the switch so that the switch is alternately in the blocking state and a conducting state.
3. Circuit according to claim 2 , wherein the alternating switching circuit is configured for applying the bias voltage to a control electrode of an injection transistor forming said switch, the injection transistor being arranged so as to form a direct injection circuit.
4. Circuit according to claim 1 , further comprising:
an additional switch connected in parallel to the terminals of the switch and
an additional circuit configured for applying an alternating voltage to a control electrode of the additional switch so as to cause the additional switch switching between a blocking state and a conducting state.
5. Method for operating comprising:
providing the detection circuit wherein a photodiode is connected to an integrator by means of a switch,
applying a first bias condition to the photodiode in order to reversely bias the photodiode during a first period and
applying a second bias condition to the photodiode in order to put the photodiode into an other state different from the reversely bias state during a second period,
wherein the switch is configured so as to be in a conducting state during the first period and in a blocking state during the second period,
wherein alternation between the first and second periods being carried out at a frequency superior to 10 Hz.
6. Method according to claim 5 , wherein:
the integrator is configured so as to apply a bias potential to one electrode of the photodiode,
a first voltage is applied to a control electrode of the switch so that the switch is in a conducting state and allows the passage of charge carriers between the photodiode and the integrator during the first period, and
a second voltage is applied to the control electrode of the switch so that the switch is in a blocking state and puts one electrode of the photodiode in a floating state during the second period.
7. Method according to claim 5 , wherein
an additional switch is connected in parallel to the terminals of the switch and
during a first portion of the first period, a first additional voltage is applied to a control electrode of the additional switch so as to put the additional switch into a conducting state and
during a second portion of the first period a second additional voltage is applied to the control electrode so as to block the passage of the current and to put the additional switch in the blocking state.