| 摘要 |
A comparator comprises a differential amplifier (T1 , T2, T8, T9) having differential inputs (IN1 , IN2) forming the comparator inputs, and a first and a second amplifier output (f1 , f2) forming the comparator outputs of a first comparator stage, wherein the differential amplifier has first (T1 , T8) and second (T2, T9) parallel branches. The comparator has a first current source circuit (32) defines a current to be driven through the differential amplifier, a second current source circuit (34) comprising a load driven by the first branch and a third current source circuit (36), comprising a load driven by the second branch. Circuitry (T6,T7) is provided for defining the voltage difference between the first and second amplifier outputs when the differential amplifier is in a stable state providing a differential output. This arrangement drives current through the two branches independently, so that the main transistors in each branch can be kept on to enable rapid response times. By fixing the voltage difference between the outputs, it is possible to remove dependency on the duty cycle on the common voltage mode of the differential amplifier. |
