题目7单选题
555定时器构成的施密特触发器其回差电压为( )A. <img src="https://tihai-oss-cloud.itihey.com/img/94cf585ef94dac1bdc52a18822b58c92.png">B. <img src="https://tihai-oss-cloud.itihey.com/img/f9748c618bf05a8b734cec081ad513f6.png">C. <img src="https://tihai-oss-cloud.itihey.com/img/44402fe097f2bf690576f4a93ca05191.png">D. <img src="https://tihai-oss-cloud.itihey.com/img/b193b3f59ebd4612c3397bf0b6743758.png">