Circuit for operating a multi-gate VIS/IR photodiode
A circuit that includes: a photodiode configured to absorb photons and to generate photo-carriers from the absorbed photons; a first MOSFET transistor that includes: a first channel terminal coupled to a first terminal of the photodiode and configured to collect a portion of the photo-carriers generated by the photodiode; a second channel terminal; and a gate terminal coupled to a first control voltage source; a first readout circuit configured to output a first readout voltage; a second readout circuit configured to output a second readout voltage; and a current-steering circuit configured to steer the photo-carriers generated by the photodiode to one or both of the first readout circuit and the second readout circuit.
1. A circuit comprising:
a photodiode configured to absorb photons and to generate photo-carriers from the absorbed photons;
a first readout circuit configured to output a first readout voltage, the first readout circuit comprising:
a first capacitor configured to integrate the photo-carriers generated by the photodiode; and
a first reset MOSFET transistor configured to charge the first capacitor to a first voltage;
a second readout circuit configured to output a second readout voltage, the second readout circuit comprising:
a second capacitor configured to integrate the photo-carriers generated by the photodiode; and
a second reset MOSFET transistor configured to charge the second capacitor to a second voltage;
a first MOSFET transistor comprising:
a first channel terminal;
a second channel terminal coupled to the first readout circuit; and
a first gate terminal coupled to a first control voltage source;
a second MOSFET transistor comprising:
a third channel terminal;
a fourth channel terminal coupled to the second readout circuit; and
a second gate terminal coupled to the first control voltage source; and
a current-steering circuit configured to steer the photo-carriers generated by the photodiode to one or both of the first readout circuit and the second readout circuit, the current-steering circuit comprising:
a first current-steering MOSFET transistor comprising a third gate terminal coupled to a second control voltage source, a fifth channel terminal coupled to a first terminal of the photodiode and configured to collect a portion of the photo-carriers generated by the photodiode, and a sixth channel terminal coupled to the first channel terminal; and
a second current-steering MOSFET transistor comprising a fourth gate terminal coupled to a third control voltage source, a seventh channel terminal coupled to the first terminal of the photodiode and configured to collect a portion of the photo-carriers generated by the photodiode, and an eighth channel terminal coupled to the third channel terminal,
wherein, during operation of the circuit, the first control voltage source generates a first control voltage configured to create a first voltage difference between the first voltage and a third voltage of the first terminal of the photodiode, and to create a second voltage difference between the second voltage and the third voltage of the first terminal of the photodiode.
2. The circuit of claim 1 , further comprising a first semiconductor layer and a second semiconductor layer,
wherein the photodiode is supported by the first semiconductor layer, and
wherein the first MOSFET transistor, the second MOSFET transistor, the first readout circuit, the second readout circuit, and the current-steering circuit are supported by the second semiconductor layer.
3. The circuit of claim 1 , further comprising a first semiconductor layer and a second semiconductor layer,
wherein the photodiode and the current-steering circuit are supported by the first semiconductor layer, and
wherein the first readout circuit, the second readout circuit, the first MOSFET transistor, and the second MOSFET transistor are supported by the second semiconductor layer.
4. The circuit of claim 1 , further comprising a first semiconductor layer and a second semiconductor layer,
wherein the photodiode, the current-steering circuit, the first MOSFET transistor, and the second MOSFET transistor are supported by the first semiconductor layer, and
wherein the first readout circuit and the second readout circuit are supported by the second semiconductor layer.
5. The circuit of claim 1 , wherein during operation of the circuit, the first control voltage is configured to operate the first MOSFET transistor and the second MOSFET transistor in a subthreshold region or a saturation region.
6. The circuit of claim 1 , wherein the first voltage difference is greater than or equal to 10% of the first voltage, and
wherein the second voltage difference is greater than or equal to 10% of the second voltage.
7. The circuit of claim 1 , wherein during operation of the circuit, the first control voltage source reduces a first dark current integrated by the first capacitor and a second dark current integrated by the second capacitor relative to a comparable circuit without the first MOSFET transistor and the second MOSFET transistor.
8. The circuit of claim 1 , wherein during operation of the circuit, the second control voltage source and the third control voltage source are controlled to operate the circuit in a time-of-flight imaging mode by steering the photo-carriers to the first readout circuit for a first period, and steering the photo-carriers to the second readout circuit for a second period.
9. The circuit of claim 1 , wherein during operation of the circuit, the second control voltage source and the third control voltage source are controlled to operate the circuit in an intensity imaging mode by steering the photo-carriers to the first readout circuit and the second readout circuit in a synchronous manner.
10. The circuit of claim 1 , wherein during operation of the circuit, the second control voltage source and the third control voltage source are controlled to operate the circuit in an intensity imaging mode by steering the photo-carriers to one of the first readout circuit and the second readout circuit while operating in the intensity imaging mode.