How to Calculate Sample Rates of Integrators

[Elliot]

Hi All. I'm trying to get my head around the humble AC integrator.

As far as I can see, it's really just a low pass filter. So when people refer to the "number of samples that are being averaged" by the integrator, I am at a loss to fully understand.

The corner frequency (fo) is 1/(2piCR2) where R2 is the bypass resistor, and C is the bypass capacitor - both across the Opamp output and input.

So, if R2 is 120k, and C is .1uf, then the corner frequency is 13.3Hz. Does this mean that the integrator is taking 13 samples per second? What about all the other samples in the cut-off band after fo?

Some help would be appreciated. Thanks in advance.

[6666]

There has been some recent talk about this Altra posted some links to topics

[6666]

maybe this if link works
https://www.geotech1.com/forums/show...082#post270082

[Qiaozhi]

Hi All. I'm trying to get my head around the humble AC integrator.

As far as I can see, it's really just a low pass filter. So when people refer to the "number of samples that are being averaged" by the integrator, I am at a loss to fully understand.

The corner frequency (fo) is 1/(2piCR2) where R2 is the bypass resistor, and C is the bypass capacitor - both across the Opamp output and input.

So, if R2 is 120k, and C is .1uf, then the corner frequency is 13.3Hz. Does this mean that the integrator is taking 13 samples per second? What about all the other samples in the cut-off band after fo?

Some help would be appreciated. Thanks in advance.

I think you're getting confused between a simple integrator and a sampling integrator. The sampling integrator includes a gating circuit (usually a jfet or a bipolar switch) that synchronously demodulates the incoming signal. Hence the reference to "number of samples".

[Elliot]

I think you're getting confused between a simple integrator and a sampling integrator. The sampling integrator includes a gating circuit (usually a jfet or a bipolar switch) that synchronously demodulates the incoming signal. Hence the reference to "number of samples".

Okay. I meant an integrator with a gating circuit before it. I've looked through the myriad threads kindly suggested by 6666 (and the referenced sub-threads), and haven't yet seen a formula to calculate the number of samples per second for the attached example circuit. I'm not worried about calculating the gain of the integrator.

[waltr]

Not simple----best is Carls post that goes sample by sample to calculate integrator output.
https://www.geotech1.com/forums/show...4582#post54582

Setup a spreedsheet with the parameters: Cs,Rs, pulse rate, Sample time, etc. Then calculate the output at each sample time.
Plot this to see the time response to an input step.

[green]

R4 and C2 set the response in your circuit. Sample rate(Tx rate) and sample time effect the gain.

[Qiaozhi]

Or simulate it with SPICE.