Current sensing circuit (30, 30i) comprising a second field-effect transistor (32, 32i) for generating a sensing current proportional to a current flowing through a working circuit (20, 20i) having a first field-effect transistor (22, 22i); a first bipolar transistor (34, 34i) and a second bipolar transistor (36, 36i) having bases connected together, wherein emitters of the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i) are respectively connected to drains of the first field-effect transistor (22, 22i) and the second field-effect transistor (32, 32i); an operational amplifier (38, 38i) having its positive input and negative input connected to collectors of the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i), respectively, and its output connected to the bases of the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i); and a third and fourth field-effect transistors (40, 40i, 42, 42i) for making currents flowing through the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i) the same, wherein a resistance of the second field-effect transistor (32, 32i) between its drain and source during conduction is larger than a resistance of the first field-effect transistor (22, 22i) between its drain and source during conduction, and wherein a drain voltage of the first field-effect transistor (22, 22i) is kept to be equal to a drain voltage of the second field-effect transistor (32, 32i) via a feedback loop formed by the first bipolar transistor (34, 34i), the second bipolar transistor (36, 36i) and the operational amplifier (38, 38i). a second field-effect transistor (32, 32i) for generating a sensing current proportional to a current flowing through a working circuit (20, 20i) having a first field-effect transistor (22, 22i); a first bipolar transistor (34, 34i) and a second bipolar transistor (36, 36i) having bases connected together, wherein emitters of the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i) are respectively connected to drains of the first field-effect transistor (22, 22i) and the second field-effect transistor (32, 32i); an operational amplifier (38, 38i) having its positive input and negative input connected to collectors of the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i), respectively, and its output connected to the bases of the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i); and a third and fourth field-effect transistors (40, 40i, 42, 42i) for making currents flowing through the first bipolar transistor (34, 34i) and the second bipolar transistor (36, 36i) the same, wherein a resistance of the second field-effect transistor (32, 32i) between its drain and source during conduction is larger than a resistance of the first field-effect transistor (22, 22i) between its drain and source during conduction, and wherein a drain voltage of the first field-effect transistor (22, 22i) is kept to be equal to a drain voltage of the second field-effect transistor (32, 32i) via a feedback loop formed by the first bipolar transistor (34, 34i), the second bipolar transistor (36, 36i) and the operational amplifier (38, 38i).