| 摘要 |
PROBLEM TO BE SOLVED: To stably perform the waveform shaping operation even in the case of input of a signal which doesn't reach an input voltage and to easily highly integrate the circuit. SOLUTION: A control circuit 9 turns on/off switches 5 and 6, and thereby, a standard reference voltage M inputted to the negative input terminal of a comparator 7 is changed to a lower voltage L only for a prescribed time when an input signal 100 crosses the reference voltage M during rise, and the reference voltage is changed to a higher voltage H only for a prescribed time when the input signal 100 crosses the reference voltage N during fall. Thus, the zero crossing Schmitt operation is performed only with one comparator; and when the voltage level of the input signal 100 is low, the control circuit 9 changes the reference voltage to two levels of voltages L and H to make the comparator temporarily perform the normal Schmitt operation, and the input signal 100 has the waveform stably shaped. |
