Feedback capacitor and method for readout of hybrid bonded image sensors
A hybrid-bonded image sensor has a photodiode die with multiple macrocells; each macrocell has at least one photodiode and a coupling region. The coupling regions couple to a coupling region of a macrocell unit of a supporting circuitry die where they feed an input of an amplifier and a feedback capacitor. The feedback capacitor also couples to output of the amplifier, and the amplifier inverts between the input and the output. The method includes resetting a photodiode of the photodiode die; coupling signal from photodiode through the bond point to the supporting circuitry die to a feedback capacitor and to an input of the amplifier, the feedback capacitor also coupled to an inverting output of the amplifier; and amplifying the signal with the amplifier, where a capacitance of the feedback capacitor determines a gain of the amplifier.
1. A hybrid bonded image sensor comprising:
a photodiode die comprising a plurality of macrocells, where each macrocell comprises at least one photodiode and a contact;
a supporting circuitry die comprising at least one macrocell unit, each macrocell unit comprising at least one contact electrically coupled to the contact of a macrocell of the photodiode die, the coupling point of the macrocell unit of the supporting circuitry die coupled to an input of an amplifier,
a first plate of a feedback capacitor coupled to the input of the amplifier, wherein a second plate of the feedback capacitor is coupled to an output of the amplifier,
wherein the amplifier inverts between the input and the output; and
the feedback capacitor has configurable capacitance, being comprised of at least a first capacitor, a second capacitor, and a selection transistor coupled in series with the second capacitor.
2. The hybrid bonded image sensor of claim 1 wherein the amplifier is a common-source amplifier.
3. The hybrid bonded image sensor of claim 2 wherein there are 2, 4, 8 or 16 photodiodes per photodiode-die macrocell.
4. The hybrid bonded image sensor of claim 2 wherein the feedback capacitor has configurable capacitance.
5. The hybrid bonded image sensor of claim 1 wherein the amplifier is a differential amplifier.
6. The hybrid bonded image sensor of claim 5 wherein there are 2, 4, 8 or 16 photodiodes per photodiode-die macrocell.
7. The hybrid bonded image sensor of claim 5 wherein the feedback capacitor has configurable capacitance.
8. The hybrid bonded image sensor of claim 1 wherein there are 2, 4, 8 or 16 photodiodes per photodiode-die macrocell.
9. A method of amplifying a signal from a photodiode of a photodiode die comprising:
resetting a photodiode of the photodiode die;
coupling a signal from the photodiode to a contact, the contact coupled to a contact of a supporting circuitry die;
coupling the signal through the contact of the supporting circuitry to a first plate of a feedback capacitor and to an input of an amplifier, where a second plate of the feedback capacitor is coupled to an inverting output of the amplifier; and amplifying the signal with the amplifier, where a capacitance of the feedback capacitor determines a gain of the amplifier;
where the feedback capacitor has configurable capacitance, being comprised of at least a first capacitor, a second capacitor, and a selection transistor coupled in series with the second capacitor.
10. The method of claim 9 where the amplifier comprises a common source amplifier.
11. The method of claim 9 wherein the amplifier comprises a differential amplifier.
12. The method of claim 9 wherein the capacitance of the feedback capacitor is determined by a capacitance selection signal, and further comprising configuring the capacitance selection signal to determine gain of the amplifier.