Question 10.7: A 555 timer is connected as a one-shot with R ext = 10 kΩ an...
A 555 timer is connected as a one-shot with R_{\mathrm{ext}}=10 \mathrm{k} \Omega \text { and } C_{\mathrm{ext}}=0.1 \mu \mathrm{F}. What is the pulse width of the output?
You can determine the pulse width in two ways. You can use either Equation (10–15) or the graph in Figure 10–43 . Using the formula,
t_W=1.1 R_{\mathrm{ext}} C_{\mathrm{ext}} (10.15)
t_W=1.1 R_{\mathrm{ext}} C_{\mathrm{ext}}=1.1(10 \mathrm{k} \Omega)(0.1 \mu \mathrm{F})=1.1 \mathrm{~ms}
To use the graph, move along the C = 0.1 mF line until it intersects with the sloped line corresponding to R = 10 kΩ. At that point, project down to the horizontal axis and you get a pulse width of 1.1 ms as illustrated in Figure 10–44 .
P R A C T I C E EXERCISE
To what value must R_{\mathrm{ext}} be changed to increase the one-shot’s output pulse width to 5 ms?
