Help please - comparing analogue to a digital FIR filter

[weedeek182]

Help please.....

Good day. Right, basically i'm doing a module at Uni, that i have no clue about, and i am in some need of help.

I am designing an analogue filter (active 2nd order LPF) and comparing it to a digital FIR filter.

I have one query that i have been trying to get an answer for, but its not exactly the type of thing you can type straight into a search engine.

Here it is: when you design the filter for analogue you represent the graph as a voltage response and when its digital it is in dB's. Is this right???
I am using Schematics from PSpice and Matlab. Is there a way to get both as voltage or in dB's.

Also, a 1st order LPF will have 2 resistors and 1 capacitor and a 2nd order has 2 resistors and 2 capacitors. Is this right??? please help!!

 

[dipnirvana]

Re: Help please.....

I suggest you read this ,

https://en.wikipedia.org/wiki/Electronic_filter

Now dB has nothing to do with if it's Analog or digital filter .And you can get results in the simulation in dB and Voltage both . Normally when you do AC analysis it gives the vertical axis as Voltage but you can change it to 20*log(Vout/Vin) that's dB.

And now your question on order , each recative element(capacitor or inductor) means order. So two capacitor means 2nd order filter, genrally speaking