# Cutoff frequency for attenuator, how to calculate

#### Thevenin99

Joined Mar 23, 2017
12
Hello I would like to know what are your opinions about how to calculate the cutoff frequency of this circuit. I basically want to have a cutoff frequency of 1 MegaHertz, which is why I have the low pass filter and I want to divide the voltage by 10 which is a simple voltage divider.

My problem is that I have looked for the right formula to calculate the cutoff frequency but I haven't found one that works. Thats why I haven't been able to calculate the right values for the capacitors in my circuit.

#### RichardO

Joined May 4, 2013
2,271
Hello I would like to know what are your opinions about how to calculate the cutoff frequency of this circuit. I basically want to have a cutoff frequency of 1 MegaHertz, which is why I have the low pass filter and I want to divide the voltage by 10 which is a simple voltage divider.

My problem is that I have looked for the right formula to calculate the cutoff frequency but I haven't found one that works. Thats why I haven't been able to calculate the right values for the capacitors in my circuit.
The impedance of the capacitors should have the same ratio as the resistors. C4 should be 1/9 the value of C5. As you can see, C5 is unrealistically small.

This looks like an oscilloscope probe to me. Is it?

Here is a lot of information on scope probes. (It is a 1MB file).
http://w140.com/tekwiki/images/6/62/062-1146-00.pdf