Star ground or ground plane

[dr.power]

Hi guys,

I would like to know when designing a PCB which method is better to be implemented (in a circuit having pre-Amp, Power Amplifiers and CMOS chips and so on) "the star ground" or the "ground plane" which the later is called polygon sometimes?
Furthermore if my assumption of the GROUND LOOP is right (I hope), then a ground plane does not create ground loops somehow?

P.S Why I am not able to find any PCB in the net having a ground loop so that I could understand it JUST right? I found this:
**broken link removed**
But it does not have PCB as well...

Thanks a lot

 

[Gobbledok]

Ground Planes generally belong on (multi-layer) PCB's. As well as providing a central ground point for the circuit, it also provides shielding from (electronic) noise. A ground loop will not be a problem on a properly designed PCB.

Star grounds generally belong on things such as car stereo's (or the whole car, the chassis being the central ground point), amplifiers and other such larger installations (such as your UAV example) to prevent ground loops.

That is my understanding anyway.

 

[cachehiker]

Assume your audio amp is in a metal case.

Assume also that your ampifier common is connected to the case and that the inputs are non-isolated RCA jacks.

If you then run a wire from the RCA ring to the input common on the PCB, that makes two connections to ground, a ground loop is created, and you end up with a nice little 60Hz hum being picked up by your preamp.

The preferability of star grounds vs. ground planes depends upon your design implementation. Round holes in the ground planes for small pads don't generally behave like ground loops and you're often dealing with the relative noise immunity of digital circuits too. Long slots for headers and long traces in ground planes behave like antennas and there are situations where they can receive enough noise to present problems although it's usually transmission that's the problem. As I understand it, they have to be really big slots to pick up very much audio frequency hum and then that hum needs to be amplified to be audible.

 

[4pyros]

If you look in some of the audio forums, you will find star grounds on amp boards.

 

[dr.power]

Thanks Guys,

Now another question arises.
I am designing a dual power supply based on 7806 and 7906, Now I do not if I should polygon the PCB of the said power supply or not?
Any idea bout pores and cones plz?

Thanks

 

[ronsimpson]

To star or not to stat.
I often use a combination of ground plane and star. In the case of a dual power supply, I might pore a ground plane around the LM7806 and a different around the LM7906. Then connect the two together at the output jack. Any time you have two different circuits it is OK to keep them separated and then connect them at one point. I can't see what you are doing! This supply is so simple I think you can do what you want. A good healthy ground never hearts. I would use ground across as much of the board as you can.

 

[dr.power]

To star or not to stat.
I often use a combination of ground plane and star. In the case of a dual power supply, I might pore a ground plane around the LM7806 and a different around the LM7906. Then connect the two together at the output jack. Any time you have two different circuits it is OK to keep them separated and then connect them at one point. I can't see what you are doing! This supply is so simple I think you can do what you want. A good healthy ground never hearts. I would use ground across as much of the board as you can.

Hi, And thanks a bunch.

I agreed that it is good to use a star ground to connect the power supply unit to the other circuits (bloacks). But I would like to see if it is a good choice to use ground plane for the power supply unit itself?

PLZ,What is your idea about the dual power supply PCb I have designed?

 

[ronsimpson]

Are you going to have 0.1uf caps on the output of the regulators?

 

[dr.power]

Are you going to have 0.1uf caps on the output of the regulators?

yes, Is it wrong doing so?

I will put the deccopling 0.1uF in the other blocks as short as to the other chips..

 

[Radioman913]

Are you going to have 0.1uf caps on the output of the regulators?

0.1uf should be on the input along with the filter cap. It is not needed on the output.
Rick