Feed-forward technique for power supply rejection ratio improvement of bit line

摘要

An image sensor read out circuit includes a first current mirror circuit in which a second current conducted through a second current path is controlled in response to a first current conducted through the first current path. The second current is conducted through an amplifier transistor of a pixel circuit. A first current source is coupled to the first current path to provide a substantially constant current component of the first current. A second current source is coupled to a power supply rail of the pixel circuit and coupled to the first current path to provide a ripple current component of the first current. The ripple current component provided by the second current source is responsive to a ripple in the power supply rail. The first current is responsive to a sum of the currents from the first and second current sources.

主权项

1. An image sensor read out circuit, comprising:
a first current mirror circuit having a first current path and a second current path, wherein a second current conducted through the second current path of the first current mirror circuit is controlled in response to a first current conducted through the first current path of the first current mirror circuit, wherein the second current path of the first current mirror circuit is coupled to an amplifier transistor of a pixel circuit of an image sensor, wherein the second current is conducted through the amplifier transistor; a first current source coupled to the first current path of the first current mirror circuit to provide a substantially constant current component of the first current; and a second current source coupled to a power supply rail of the pixel circuit and coupled to the first current path of the first current mirror circuit to provide a ripple current component of the first current, wherein the ripple current component provided by the second current source is responsive to a ripple in the power supply rail, wherein the first current is responsive to a sum of the substantially constant current component provided by the first current source and the ripple current component provided by the second current source.