An apparatus comprising: a passive array of resistive elements; a row selector switch configured to connect a current source to a particular row of resistive elements of the passive array; a column selector switch configured to connect a particular column of resistive elements of the passive array to ground; and a feedback column selector switch configured to connect all columns of resistive elements to a voltage source, except for the particular column connected to ground by the column selector switch; the voltage source configured to apply a voltage to the columns of resistive elements connected to the voltage source, the voltage matching a voltage dropped over the resistive element connected in circuit by the row selector switch and column selector switch; and further comprising one or more of: a row selector switch compensation circuit (220, 320) connected between the current source and the passive array of resistive elements, the row selector switch compensation circuit configured to apply a voltage across a row dummy element equal and opposite to a voltage dropped over the row selector switch; a column selector switch compensation circuit (240, 340) connected between the passive array of resistive elements and ground, the column selector switch compensation circuit configured to apply a voltage across a column dummy element equal and opposite to a voltage dropped over the column selector switch; and a feedback column selector switch compensation circuit (260, 360) connected between the current source and the passive array of resistive elements, the feedback column selector switch compensation circuit configured to apply a voltage across a feedback column dummy element equal and opposite to a voltage dropped over the feedback column selector switch. a passive array of resistive elements; a row selector switch configured to connect a current source to a particular row of resistive elements of the passive array; a column selector switch configured to connect a particular column of resistive elements of the passive array to ground; and a feedback column selector switch configured to connect all columns of resistive elements to a voltage source, except for the particular column connected to ground by the column selector switch; the voltage source configured to apply a voltage to the columns of resistive elements connected to the voltage source, the voltage matching a voltage dropped over the resistive element connected in circuit by the row selector switch and column selector switch; and further comprising one or more of: a row selector switch compensation circuit (220, 320) connected between the current source and the passive array of resistive elements, the row selector switch compensation circuit configured to apply a voltage across a row dummy element equal and opposite to a voltage dropped over the row selector switch; a column selector switch compensation circuit (240, 340) connected between the passive array of resistive elements and ground, the column selector switch compensation circuit configured to apply a voltage across a column dummy element equal and opposite to a voltage dropped over the column selector switch; and a feedback column selector switch compensation circuit (260, 360) connected between the current source and the passive array of resistive elements, the feedback column selector switch compensation circuit configured to apply a voltage across a feedback column dummy element equal and opposite to a voltage dropped over the feedback column selector switch. a row selector switch compensation circuit (220, 320) connected between the current source and the passive array of resistive elements, the row selector switch compensation circuit configured to apply a voltage across a row dummy element equal and opposite to a voltage dropped over the row selector switch; a column selector switch compensation circuit (240, 340) connected between the passive array of resistive elements and ground, the column selector switch compensation circuit configured to apply a voltage across a column dummy element equal and opposite to a voltage dropped over the column selector switch; and a feedback column selector switch compensation circuit (260, 360) connected between the current source and the passive array of resistive elements, the feedback column selector switch compensation circuit configured to apply a voltage across a feedback column dummy element equal and opposite to a voltage dropped over the feedback column selector switch.