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

 

It's approximately 0.7*R4*C4.

 

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.

 

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

 

It's approximately 0.7*R4*C4.

Thanks crutschow.