| 摘要 |
A low noise apparatus for receiving an input current and producing an output current which mirrors the input current significantly increases accuracy and signal-to-noise ratio by greatly reducing the effects resulting from threshold voltage mismatches and 1/f noise. The apparatus comprises two cascode current mirrors. Further, the apparatus comprises a switching network which, in turn, comprises a plurality of switches formed within either a first or second electrical path. A first clock controls the switches formed within the first electrical path, while a second clock controls the switches formed within the second electrical path. When the first clock is in its first state and the second clock is in its second state, the switches formed within the first electrical path close to form the first cascode current mirror. However, the switches formed within the second electrical path remain open. Conversely, when the first clock is in its second state and the second clock is in its first state, the switches formed within the second electrical path close to form the second cascode current mirror. However, the switches formed within the first electrical path remain open. Consequently, the apparatus modulates a significant percentage of the threshold voltage mismatch up to the operating frequency of the two clocks. As a result, the first order error term resulting from the threshold voltage mismatch is eliminated and 1/f noise is reduced.
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