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现有国产超声波诊断仪中使用半导体闸流管作脉冲发射管的,几乎都是选用3CT5(5A/500V)高频可控硅,其典型线路如图1所示。为保证仪器的探测灵敏度,A、B间最高电压要在420V以上,这就要求BG_(104)的漏电流小于0.3mA。但3CTSF可控硅其漏电流大至3mA时仍为合格品。许多正品可控硅因漏电流大,影响超声波诊断仪的灵敏度,而不能充当脉冲发射管。是不是可以用漏电流小的小功率可控硅来代替呢?
The existing domestic ultrasonic diagnostic apparatus using a thyristor for pulse launch tube, almost all use 3CT5 (5A / 500V) high frequency SCR, the typical line shown in Figure 1. To ensure the detection sensitivity of the instrument, the maximum voltage between A and B should be over 420V, which requires that the leakage current of BG_ (104) is less than 0.3mA. But the 3CTSF SCR leakage current is still as good as 3mA. Many genuine thyristor due to leakage current, the sensitivity of ultrasonic diagnostic apparatus, and can not act as a pulse tube. Is it possible to use small leakage SCR small power SCR instead?