An output compensation circuit (120, 220, 320, 420, 520) of an image sensor comprising:: a first current mirror circuit (222, 322), coupled to a select transistor of a pixel circuit (P 11 -P MN) of the image sensor, the first current mirror circuit being configured to, in response to a first current, generate a second current flowing through the select transistor to compensate for a variation in a signal level of a sensor output of the pixel circuit (P 11 -P MN) caused by variation of a first power supply voltage (VDD_P), wherein the image sensor comprises a row controller which controls the select transistor, when a control terminal (N CR) of the select transistor is coupled to the first power supply voltage (VDD_P) through an equivalent resistor (Ron), the select transistor is turned on, the first current mirror circuit (222, 322) is configured to generate the second current flowing through the select transistor, and the pixel circuit (P 11) outputs the second current through the select transistor; a first current generator circuit (224, 324, 524), supplied by the first power supply voltage (VDD_P) and coupled to the first current mirror circuit (222, 322), the first current generator circuit being configured to output a compensation current to the first current mirror circuit (222,322) in response to a variation in the first power supply voltage (VDD_P), the compensation current serving as a first portion of the first current; and a second current generator circuit, coupled to the first current mirror circuit (222, 322), the second current generator circuit being supplied by a second power supply voltage and uncoupled from the first power supply voltage (VDD_P) supplied to the pixel circuit (P 11 -P MN), the second current generator circuit being configured to output a reference current to the first current mirror circuit (222, 322), the reference current serving as a second portion of the first current. a first current mirror circuit (222, 322), coupled to a select transistor of a pixel circuit (P 11 -P MN) of the image sensor, the first current mirror circuit being configured to, in response to a first current, generate a second current flowing through the select transistor to compensate for a variation in a signal level of a sensor output of the pixel circuit (P 11 -P MN) caused by variation of a first power supply voltage (VDD_P), wherein the image sensor comprises a row controller which controls the select transistor, when a control terminal (N CR) of the select transistor is coupled to the first power supply voltage (VDD_P) through an equivalent resistor (Ron), the select transistor is turned on, the first current mirror circuit (222, 322) is configured to generate the second current flowing through the select transistor, and the pixel circuit (P 11) outputs the second current through the select transistor; a first current generator circuit (224, 324, 524), supplied by the first power supply voltage (VDD_P) and coupled to the first current mirror circuit (222, 322), the first current generator circuit being configured to output a compensation current to the first current mirror circuit (222,322) in response to a variation in the first power supply voltage (VDD_P), the compensation current serving as a first portion of the first current; and a second current generator circuit, coupled to the first current mirror circuit (222, 322), the second current generator circuit being supplied by a second power supply voltage and uncoupled from the first power supply voltage (VDD_P) supplied to the pixel circuit (P 11 -P MN), the second current generator circuit being configured to output a reference current to the first current mirror circuit (222, 322), the reference current serving as a second portion of the first current.