Patent ID: 7057463
Filing Date: 2006-06-06
Classification: H03F

Abstract:
1. An amplifier which amplifies an input signal, comprising: an input stage which receives the input signal; a plurality of amplifier stages each having a gain smaller than a target gain, wherein the input stage includes a pair of differential input terminals for receiving the input signal; the plurality of amplifier stages are connected in parallel, divide a current proportional to the input signal, subject divided currents to differential amplification, and add output currents obtained from their respective amplifications to achieve the target gain as a whole; at least one of the plurality of amplifier stages including a first current mirror circuit and a second current mirror circuit each of which amplifies the divided current by a gain of x, and a third current mirror circuit and a fourth current mirror circuit which amplify currents amplified by the first current mirror circuit and the second current mirror circuit respectively, by a gain of y, and wherein gains of the first through fourth current mirror circuits are designed such that a product of x and y is n/2, wherein n denotes the target gain.