Abstract: A current source circuit that operates advantageously in the linear region of an FET and that minimizes any voltage drop at its output node which is not load related. The circuit operates under the principle that the output current is dynamically measured without introducing any elements that affects the voltage drop across the FET. Its current source includes a pass device with feedback control, such that a constant current is obtained regardless of the load placed at the output terminal. The operation of the pass device is mirrored by a second pass device having physical dimension that only a fraction of those of the first pass device. A high input impedance differential amplifier, driven by the respective outputs of the first and second pass devices, forces the mirror pass device to the identical voltage as the first pass device.