hi SBR,
         for any stable circuit  Power=k*SNR*BW,you can verify this for some passive filter (k is a constant will different for different circuits).

Thanks,
Rajasekhar.

hi Aaron,
              i donno about THD  but i assumed that SNR is same as dynamic range.
Take a simple rc low pass filter: SNR=v*v*/kt     bw=1/r*c     power=v*v/r....so you can verify the rule what i have given. And i learned this from one of tsividies  student thesis ,there he has proven this simple example analytically and for some big ckts like 2nd order system through simulation. if you are interested i will send you the thesis.

Thanks,
Rajasekhar.

Hi guys,


from my understanding, dynamic range is the range of values which the signal can take and provide a useful output. At the low end it is limited by noise and at the high end it is limited by distortion. That's where I got the relationship. But I'm not really sure if its defined exactly right. And also you should be careful when you use the word SNR since I believe some people use it to mean the ratio of signal power to noise power where noise is from random sources such as flicker noise and thermal noise, while some people use SNR to mean signal power to any unwanted power such as flicker noise and unwanted harmonics and interference.

I'm quite interested in the result Rajasekar. Could you give me the name of the student and i'll try and find his thesis. No need to send it to me. I think i've seen a relationship like what you wrote but i don't remember it too well...


thanks,
Aaron

Hi Rajasekar,
   Thanks for the reference.

Best Regards,
SBR

Hi Rajasekar,
 My understanding for dynamic range is the ratio of highest and lowest signal level in the circuit. and SNR is the ratio of signal level to the noise level.
But I heard most people say DR is same as SNR, which I was bit confused.

Thanks,
S.Baanurathan

Hi Rajasekhar and SBR,


thanks for sharing.

For the equation derived in the appendix it has two problems. In passive filters we don't really talk about power dissipation, although the equation may be correct. For active filters, orders of magnitude doesn't begin to decribe how far off the equation could be. For example A.19,

Pi = 8kTf₀S/N

Let S/N = 10 and f0 = 1 MHz. Then Pi = 3.2016*10^-13 W. I haven't heard of an active filter operating with less than the order of microwatts. The problem comes from the authors use of an output swing of Vdd which almost never happens in active filters.

BTW the author mentions

Quote:


So DR is basically a ratio of two signal strengths while SNR is the ratio of signal to noise strength. In my opinion it makes sense that if you want an overall SNR of 20 dB, then the maximum signal strength gives THD of 20 dB and minimum gives SNR (where N is random noise) of 20 dB.

Anyway overall the thesis looks quite interesting so thanks for sharing. I will have a look.


cheers,
Aaron

Hi Rajasekhar,


I usually take power consumption to mean the amount of battery (or whatever supply) power used. Power consumption is especially important in design for mobile applications which rely on batteries.

When I think passive filters, I usually think LC type (or microwave) filters which are commonly used as band-select filters and even image-reject filters. Such filters don't consume any power at all from the battery. There is some insertion loss but it is usually kept at a minimum...

I'm not really sure what other type of passive filters people use. Sorry if i'm being confusing here. I'll take a look at the thesis but it will take me some time as i'm quite busy.


cheers,
Aaron


EDIT: I just realised this thesis is about companding filters. Maybe the fomulae are correct....will keep reading.