| 摘要 |
Long-tailed pair connections of MOSFET's are used as voltage comparators, the input stages of operational amplifiers, and other circuitry where their nearly infinite gate impedances can reduce the loading upon preceding circuitry. As conventionally operated, the tail current caused to flow through the interconnected source electrodes of the MOSFET's is sufficient to bias them such that their source-to-gate voltages exceed a threshold voltage, and the input voltage offset error of the long-tailed MOSFET pair is likely to be higher than that of most long-tailed bipolar transistor pairs. By selecting a tail current that is sufficiently small to operate a long-tailed MOSFET pair such that their source-to-gate voltages are in the sub-threshold region, the MOSFET's exhibit exponential drain current versus source-to-gate characteristics which result in markedly reduced input offset voltage error. |
