This paper presents a comprehensive study of a negative feedback mechanism in the bipolar Wilson current mirror, which is one of the most popular current mirrors used in electronic circuit designs. Although the operation of the Wilson current mirror has been covered in most microelectronic circuit design textbooks, its unusual negative feedback mechanism is still largely obscure. As a result, attempts to calculate the output resistance of the Wilson current mirror using classical negative feedback analysis have usually given the answer that is inconsistent with the correct answers obtained from direct analysis. We believe that this is probably the main reason why the negative feedback analysis of the Wilson current mirror is mostly ignored in the literature. In this paper, we aim to disclose the hidden subtleties of the Wilson current mirror by shedding a new light on its dual-loop negative feedback operation. It is shown in the paper that by doing so, we will be able to apply the negative feedback theory to the Wilson current mirror and correctly calculate its current gain and port resistances.
['Jirayuth Mahattanakul', 'Sitthichai Pookaiyaudom', 'Chris Toumazou']
Understanding Wilson current mirror via the negative feedback approach