Author Topic: Need help with power rating for active equalizer components  (Read 891 times)

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Offline hummusdudeTopic starter

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I'm building this 5 band active EQ for my home hi fi. I'm putting together a PCB and because I'm making it stereo there are a lot of passive components. Although I have minimal experience using SMD parts I starting thinking this may be the way to go to keep the size of the board from getting too big. But then it occurred to me that since this isn't a strict logic circuit that the power rating could be a factor. I'm comfortable with small circuit analysis but this one is quite complex for my experience. I'm not at all confident I could figure out the max power draw, or potential current hot spots that need a little more capacity. Is there a rule of thumb for this sort of circuit?
 

Offline dmendesf

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Re: Need help with power rating for active equalizer components
« Reply #1 on: June 28, 2020, 03:58:45 am »
Your ICs will consume like 10mA each, not a big deal. You can use 0603 resistors and capacitors. Large value capacitors may be better served by 0805 size.
 

Offline jdthorpe

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Re: Need help with power rating for active equalizer components
« Reply #2 on: July 02, 2020, 08:20:44 am »
So, it looks like the Vs+ and Vs- for the opamps are left out (for brevity), but one thing I think might
be an error is highlighted in in green in the attached schema. My read is that the highlighted node should not be
connected, but I'm a total noob so I'd be equally happy to find out that I'm wrong
 

Offline hummusdudeTopic starter

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Re: Need help with power rating for active equalizer components
« Reply #3 on: July 07, 2020, 05:12:54 am »
Great observation. I have to agree it seem odd that the virtual ground would be tied to the output of the input buffer.
 

Offline hummusdudeTopic starter

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Re: Need help with power rating for active equalizer components
« Reply #4 on: July 07, 2020, 06:03:58 am »
Also wondering if it's necessary to keep signal ground and power ground separate in a low power circuit like this. I know it's good practice on a power amp to prevent ground loop hum issues, but this is very low gain so not sure if that matters. The person who made the schematic seems to have gone out of his way to show signal ground and power ground as separate.
 

Offline jdthorpe

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Re: Need help with power rating for active equalizer components
« Reply #5 on: July 12, 2020, 12:50:38 am »
The virtual ground is held at 6v (b/c of the 100K resistors), which is (for example) connected to the reference pin (pin 3) of IC3(B) opamp.  I believe this is important because the power pins (4 and 8 ) are connected to 0 and 12v, and the bandpass circuit requires that the voltage on the reference pin of the op amp be half way between the power pins... 
« Last Edit: July 12, 2020, 06:38:13 pm by jdthorpe »
 
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