The limitations of schmitt toggle circuit , composed of 555 timing circuit , is discussed , a improved schmitt toggle circuit is given , and proved by using theory and experiment 摘要論述了常用555定時器構(gòu)成的施密特觸發(fā)器電路的局限性,給出了施密特觸發(fā)器的改進(jìn)電路,并用理論和實驗加以證明和驗證。