Light receiving circuit
View Patent ↗The light receiving circuit includes: a photoelectric conversion element for causing a current corresponding to an amount of incident light to flow; a MOS transistor including a source connected to the photoelectric conversion element and a drain connected to a node, for causing the current of the photoelectric conversion element to flow to the node while maintaining a voltage of the source to a first voltage; a reset circuit for causing a current to flow from the node to a GND terminal so that a voltage of the node becomes a second voltage lower than the first voltage; a control circuit for outputting a reset signal to the reset circuit; and a voltage increase detection circuit for detecting a fluctuation in the voltage of the node and outputting a detection result.
1. A light receiving circuit, comprising:
a photoelectric conversion element for causing a current corresponding to an amount of incident light to flow;
a MOS transistor including a source connected to the photoelectric conversion element and a drain connected to a node, for causing the current of the photoelectric conversion element to flow to the node while maintaining a voltage of the source to a first voltage;
a reset circuit for causing a current to flow from the node to a GND terminal so that a voltage of the node becomes a second voltage lower than the first voltage;
a control circuit for outputting a reset signal to the reset circuit; and
a voltage increase detection circuit for detecting a fluctuation in the voltage of the node and outputting a detection result,
the reset circuit being configured to cause, when the reset signal of the control circuit is input, the current to flow from the node to the GND terminal so that the voltage of the node becomes the second voltage, and to hold this state when the reset signal is no longer input.
2. A light receiving circuit according to claim 1 , wherein:
the reset circuit includes a reset terminal connected to the node and an input terminal connected to an output terminal of the voltage detection circuit;
the reset circuit comprises:
a low-threshold NMOS transistor including a drain connected to the reset terminal, a source connected to the GND terminal, and a gate connected to the GND terminal via a capacitor; and
a PMOS transistor including a source connected to the reset terminal, a drain connected to a gate of the low-threshold NMOS transistor, and a gate connected to the input terminal; and
the PMOS transistor is turned on when the detection signal of the voltage detection circuit is input to the input terminal.
3. A light receiving circuit according to claim 1 , wherein the photoelectric conversion element comprises a PN diode, including an N-type terminal connected to the GND terminal and a P-type terminal connected to a source of the MOS transistor.
4. A light receiving circuit according to claim 2 , wherein the photoelectric conversion element comprises a PN diode, including an N-type terminal connected to the GND terminal and a P-type terminal connected to a source of the MOS transistor.