A PTAT circuit includes a first, second, third, and fourth transistors plus a resistor. The first and second transistors have control terminals coupled to each other. The third and fourth transistors have control terminals coupled to each other. The third transistor sources a first current to the first transistor and the fourth transistor sources a second current to the second transistor. The resistor is coupled at a node to the second transistor. A current source circuit sources additional current into the node that is derived from the first and second currents. In one implementation, the additional current is a scaled mirror of the second current. In another implementation, the additional current is a scaled mirror of the sum of the first and second currents. An output current is obtained by mirroring one of the first-third currents. A band-gap output voltage is obtained by applying the additional current across a resistance.