Charge-to-voltage conversion circuit with inline amplification

An active pixel sensor (APS) readout circuit comprising:

• a floating diffusion transistor powered by a supply voltage and configured, when activated by a bias current, to produce an output voltage based on a charge detected by a light detection element associated with a pixel of an array of pixels;
• a biasing current source electrically connected to the floating diffusion transistor and configured to generate the bias current to activate the floating diffusion transistor;
• a row select transistor configured, when enabled, to connect the output voltage onto a shared pixel readout node associated with a column of the pixel within the array of pixels;
• and
• an inline amplifier stage positioned between the floating diffusion transistor and the biasing current source, the inline amplifier stage configured to use the bias current generated by the biasing current source to activate an amplifier transistor within the inline amplifier stage to amplify the output voltage on an output voltage node of the APS readout circuit.

A method comprising:

• receiving a charge at a floating diffusion transistor, the floating diffusion transistor powered by a supply voltage;
• generating, by a biasing current source electrically connected to the floating diffusion transistor, a bias current to:
• activate the floating diffusion transistor, and
• activate an amplifier transistor within an inline amplifier stage positioned between the floating diffusion transistor and the biasing current source, the amplifier transistor being configured to amplify an output voltage on an output voltage node;
• and
• producing, by the floating diffusion transistor when activated by the bias current, the output voltage based on the charge.