| 摘要 |
PURPOSE:To obtain a comparison level with high accuracy by forming a current flowing to a comparator from a signal source side with an active element equivalent to an active element constituting the comparator and cancelling the said current with an equivalent current obtained from the said element so as to block generation of an input offset voltage of the comparator. CONSTITUTION:The comparator 30 comprises Trs 32, 34 and Trs 38, 40 as active loads and the comparator 30 is added with current operating circuits 50, 52 forming currents equal to currents IB1, IB2 flowing from the signal source side. The circuits 50, 52 detect output currents I1, I2 of the comparator 30 from the Trs 32, 34 to form the currents IB1, IB2 flowing to the base of the Trs 32, 34. In this case, the Trs 32 and 60, and the Trs 34 and 78 are formed equivalently. As a result, the flowing of currents IB1, IB2 from a capacitor 28 or a phase comparator 28 being the signal source side is blocked and generation of the voltage drop by resistors 10, 14 and the currents IB1, IB2 is blocked. Then generation of an input offset voltage between bases of the Trs 32, 34 is blocked and variance in the comparison level is suppressed. |
