| 摘要 |
PURPOSE:To form a comparator which has hysteresis characteristics for setting a threshold voltage accurately by supplying reference voltage to the inverted or uninverted input terminal of an operational amplifier through a switch element. CONSTITUTION:An input voltage Vin is supplied to the inverted input terminal 1b of the operational amplifier 1 and a reference voltage VR is supplied to the uninverted input terminal 1a of an (n) channel switch MISFETQ1. Further, the other reference voltage VR' is supplied to the uninverted input terminal 1a similarly through an (n) channel switch MISFETQ2. Then, the switching MISFETs Q1 and Q2 are turned on and off complementarily by the output voltage Vout of the operational amplifier 1 and a negative-phase signal obtained by inverting the output Vout of the operational amplifier 1 through an inverter 2. Consequently, a current path is cut off and no current flows until comparison is completed, so the reference voltage never varies. Further, the reference voltage does not show any variance due to the variance of the precision between the MISFETs Q1 and Q2, so the comparison is carried out accurately. |
