Two stage amplifier readout circuit in pixel level hybrid bond image sensors
A hybrid bonded image sensor has a photodiode die with macrocells having at least one photodiode and a bond contact; a supporting circuitry die with multiple supercells, each supercell having at least one macrocell unit having a bond contact coupled to the bond contact of a macrocell of the photodiode die. Each macrocell unit lies within a supercell and has a reset transistor adapted to reset photodiodes of the macrocell of the photodiode die. Each supercell has at least one common source amplifier adapted to receive signal from the bond contact of a selected macrocell unit of the supercell, the common source amplifier coupled to drive a column line through a selectable source follower. In embodiments, the common source amplifiers of several supercells drive the selectable source follower through a distributed differential 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 bond contact;
a supporting circuitry die comprising a plurality of supercells, each supercell comprising at least one macrocell unit, each macrocell unit comprising at least one bond contact electrically connected to the bond contact of a macrocell of the photodiode die and a precharge transistor adapted to provide a precharge to photodiodes of the macrocell of the photodiode die;
each supercell comprising at least one common source amplifier adapted to receive signal from the bond contact of a selected macrocell unit of the supercell, the common source amplifier coupled to drive a column bit line through a selectable source follower.
2. The hybrid bonded image sensor of claim 1 wherein the at least one common source amplifier of each supercell is a distributed common source amplifier having an amplifier input transistor and a selection transistor for each macrocell unit and further comprising a common load.
3. The hybrid bonded image sensor of claim 2 wherein the at least one common source amplifier of each supercell further comprises a capacitor coupled between an output of the common source amplifier and the bond contact of the selected macrocell unit of the supercell.
4. The hybrid bonded image sensor of claim 3 wherein the common source amplifier is coupled to the selectable source follower through a differential amplifier, and wherein a noninverting input of the differential amplifier receives an output of the common source amplifier.
5. The hybrid bonded image sensor of claim 4 wherein the differential amplifier is a distributed differential amplifier having a separate noninverting input for each of a plurality of supercells and a common load.
6. A camera system incorporating the image sensor of claim 5 the image sensor further comprising at least one decoder coupled to drive photodiode select lines of macrocells of the array, to supercell select lines, and column select lines, the camera system further comprising:
an analog-to-digital converter coupled to receive data from the image sensor,
at least one counter coupled to the at least one decoder, and
a digital processor coupled to receive data from the analog-to-digital convertor; and
wherein the analog-to-digital convertor, counter, and image processor are formed in the supporting circuitry die.
7. The hybrid bonded image sensor of claim 4 wherein the differential amplifier further comprises a first gain-controlling capacitor coupled between an output of the differential amplifier and a noninverting input of the differential amplifier, and a second gain-controlling capacitor coupled to noninverting input of the differential amplifier.
8. A camera system incorporating the image sensor of claim 2 , the image sensor further comprising at least one decoder coupled to drive photodiode select lines of macrocells of the array, to supercell select lines, and column select lines, the camera system further comprising:
an analog-to-digital converter coupled to receive data from the image sensor,
at least one counter coupled to the at least one decoder, and
a digital processor coupled to receive data from the analog-to-digital convertor;
wherein the analog-to-digital convertor, counter, and image processor are formed in the supporting circuitry die; and
wherein the photodiode die is configured for backside illumination.