# Delayed Pulse Circuit

#### maker_2023

Joined Nov 20, 2023
173
Hi:

I have breadboarded a simple circuit that produces a delayed pulse, using a CD4011BE.
I have attached the schematic and the scope images. I would like to know how to determine the time delay.

Thanks
M

#### Attachments

• 28.3 KB Views: 19
• 18.9 KB Views: 18
• 24.1 KB Views: 17
• 24.2 KB Views: 16
Last edited:

#### crutschow

Joined Mar 14, 2008
34,845
It's approximately 0.7*R4*C4.

#### dl324

Joined Mar 30, 2015
17,152
I would like to know how to
determine the time delay.
The output of U4A will change when the input with the RC delay rises to the minimum value for a HIGH input. For CD4011 operating at 5V, that's typically 2.75V, but it could be as high as 3.5V.

Using the typical value:
$$\large V_f=V_i(1-e^{\frac{-t}{RC}})$$
$$\large t=-RCln(1-\frac{V_f}{V_i}) =-(10k\Omega)(10pF)ln(1-\frac{2.75V}{5V}) = 80ns$$
Or 0.8RC for typical and 1.2RC for maximum.

Last edited:

#### maker_2023

Joined Nov 20, 2023
173
The output of U4A will change when the input with the RC delay rises to the minimum value for a HIGH input. For CD4011 operating at 5V, that's typically 2.75V, but it could be as high as 3.5V.

Using the typical value:
$$\large V_f=V_i(1-e^{\frac{-t}{RC}})$$
$$\large t=-RCln(1-\frac{V_f}{V_i}) =-(10k\Omega)(10pF)ln(1-\frac{2.75V}{5V}) = 80ns$$
Or 0.8RC for typical and 1.2RC for maximum.
Thanks Dennis