TL = 0.69 x RB x C
= 0.69 x 150 x 10
3
x 0.01 x 10
-6
= 1 msec
TH = 0.69 x (RA + RB) x C
= 0.69 x 9250 x 10
3
x 0.01 x 10
-6
= 64 msec
IC2 组成超声波载波信号发生器。由 IC1 输出的脉冲信号控制,输出
1ms 频率 40kHz,占空比 50%的脉冲,停止 64ms。计算公式如
下:
条件: RA =1.5KΩ、 RB=15KΩ、 C=1000pF
TL = 0.69 x RB x C
= 0.69 x 15 x 10
3
x 1000 x 10
-12
= 10μsec
TH = 0.69 x (RA + RB) x C
= 0.69 x 16.5 x 10
3
x 1000 x 10
-12
= 11μsec
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