思考题与习题
6-1已知图T6-1所示为施密特触发器输入信号uI的波形，请对应画输出信号uO 的波 形。
![](https://wkrtcs.bdimg.com/rtcs/image?w=349.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_5","w":"349.00","h":"108.00","dataType":"png","c":"word/media/image1.png","imgOriW":2911,"imgOriH":903})
图T6-1
![](https://wkrtcs.bdimg.com/rtcs/image?w=318.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_10","w":"318.00","h":"205.00","dataType":"png","c":"word/media/image2.png","imgOriW":546,"imgOriH":352})
6-2 在如图6-14所示的单稳态触发器电路中，已知R=10kΩ、C=0.1μF ，G1的输出 电阻可忽略不计，试估算输出波形uO的脉冲宽度。
![](https://wkrtcs.bdimg.com/rtcs/image?w=112.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_2","w":"112.00","h":"40.00","dataType":"gif","c":"word/media/image3.gif"})
代入得，脉宽tw=0.7ms
6-3图T6-3所示电路是用两个集成单稳态触发器74121构成的脉冲波形变换电路，试 计算uO1和uO2输出脉冲的宽度，并画出对应于uI的uO1和uO2波形。
![](https://wkrtcs.bdimg.com/rtcs/image?w=552.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_5","w":"552.00","h":"190.00","dataType":"png","c":"word/media/image4.png","imgOriW":4599,"imgOriH":1583})
图T6-3
![](https://wkrtcs.bdimg.com/rtcs/image?w=289.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_10","w":"289.00","h":"229.00","dataType":"png","c":"word/media/image5.png","imgOriW":341,"imgOriH":270})
6-4图T6-4所示电路为可控多谐振荡器，已知tW等于振荡器输出脉冲周期的5倍， 请对应uk画uO1和uO2的波形。
![](https://wkrtcs.bdimg.com/rtcs/image?w=468.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_5","w":"468.00","h":"129.00","dataType":"png","c":"word/media/image6.png","imgOriW":3902,"imgOriH":1079})
图T6-4
![](https://wkrtcs.bdimg.com/rtcs/image?w=310.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_10","w":"310.00","h":"150.00","dataType":"png","c":"word/media/image7.png","imgOriW":648,"imgOriH":313})
6-5试构成一个如图6-23所示的RC环形振荡器电路，要求振荡器输出信号的频率为 1kHZ，请估算R和C的数值。若要求振荡频率为1HZ，则R和C又该为多少？
解：T≈2.2RC，f=1KHZ，则T=1ms，因此，当f=1KHZ时，RC=0.45ms；当f=1HZ时，RC=0.45s。
6-6试用555定时器构成一个单稳态电路，要求输出脉冲幅度≥10V，输出脉冲宽度在
1-10秒范围内连续可调。
解：根据题意，用555定时器设计得单稳态触发器取R1=22K,R2=18K，分压后输入端电压为6.75V(电源电压为15V），一般的，555定时器得输出高电平不低于其电源电压得90%，因此选15v.则UO输出脉宽tW=1.1RC
设C=1000μF,则
1≤1.1R×1000×10-6≤ 10
909≤R≤9K
6-7图T6-7是用两个555定时器接成的延迟报警器。当开关S断开后，经过一定的延 迟时间后扬声器开始发出声音。如果在延迟时间内S重新闭合，扬声器不会发出 声音。在图中给定的参数下，试求延迟时间的具体数值和扬声器发出声音的频率。 图中的G1是CMOS反相器，电源电压为12V。
![](https://wkrtcs.bdimg.com/rtcs/image?w=439.00&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_0","w":"439.00","h":"182.00","dataType":"jpeg","c":"word/media/image8.jpeg","imgOriW":1006,"imgOriH":417})
图T6-7
解：首先从555定时器2构成的多谐振荡器分析，其频率f为
![](https://wkrtcs.bdimg.com/rtcs/image?w=396.8&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_9","w":"396.8","h":"83.2","dataType":"png","c":"word/media/image9_1.png","imgOriW":2962,"imgOriH":616})
振荡器1的输出经过非门接至振荡器2的复位端，因此当单稳态1输出低电平时2振荡，输出高电平时2停止振荡。因此其延迟时间即单稳态的![](https://wkrtcs.bdimg.com/rtcs/image?w=27.2&md5sum=8eecdb6ed009001bd543b9d56fb6a97b&sign=74d782004a&rtcs_flag=1&rtcs_ver=4&l=webapp&bucketNum=533&ipr={"t":"img","r":"r_9","w":"27.2","h":"30.4","dataType":"png","c":"word/media/image10_1.png","imgOriW":1786,"imgOriH":989})
。
=1.1RC=11s
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