A low‐noise high output impedance DC current source

The paper proposes a structure of a new low noise high output impedance DC current source which acts as a quasi‐ideal source for frequencies lower than 10 kHz. It uses a feed‐back structure with low noise operational amplifiers. The DC current, the small signal output impedance and the noise level are controlled by the value of one single resistance. The performances of our structure are compared with the ones of the simple current source that consists in a voltage source and a resistance in series. It is shown that our structure exhibits the same noise level whereas the output impedance can be one thousand time higher.