Patent ID: 7952333

Claim:
A circuit for determining the current in a load, the circuit comprising: first and second transistors, each having a main current path and a control terminal, the main current paths each operably connected in parallel between the load and a common reference point and the control terminals being connected together; and means for setting the voltage across the main current path of the second transistor to a voltage level corresponding to a predetermined portion of the voltage across the main current path of the first transistor, control circuitry for setting the voltage across the main current path of the second transistor, the control circuitry being powered by a single supply voltage that is positive with respect to the common reference point, wherein the control circuitry includes a control transistor having a main current path connected in series between the main current path of the second transistor and the common reference point, wherein the control circuitry comprises means for providing a signal for controlling the control transistor, the signal being dependent on the error between the voltage across the main current path of the second transistor and said voltage level, and wherein the signal providing means comprises a differential amplifier in an operational amplifier arrangement further including, a first input terminal connected to a node arranged in series between the second transistor and the control transistor; and a second input terminal connected to a potential divider arrangement.