# Ground plane in audio amplifier?

• 8th November 2019, 15:31
northumber82
Ground plane in audio amplifier?
Hello, a question: can a ground plane, create problems in power audio amplifiers?

Example: if touching the input with the tip of whatever, the amplifier oscillates, can it be the fault of the ground plane? (Which is on both layers, bottom and top) Or is it because the amplifier is unstable?
• 8th November 2019, 15:53
barry
Re: Ground plane in audio amplifier?
The amplifier is obviously unstable. But is it because of the plane? Perhaps the additional capacitance of the plane is the problem. You need to analyze the circuit a little more closely, considering the plane caoacitance.
• 8th November 2019, 16:01
northumber82
Re: Ground plane in audio amplifier?
Quote:

Originally Posted by barry
The amplifier is obviously unstable. But is it because of the plane? Perhaps the additional capacitance of the plane is the problem. You need to analyze the circuit a little more closely, considering the plane caoacitance.

Thank you for the answer.
• 8th November 2019, 17:36
Riphagen
Re: Ground plane in audio amplifier?
What is your amplifier IC , grounding method is important
ex: star grounding
• 8th November 2019, 18:02
KlausST
Re: Ground plane in audio amplifier?
Hi,

Quote:

can it be the fault of the ground plane? (Which is on both layers, bottom and top)
Many unexperienced people "fill" the spaces between traces and think this now is a GND layer. But it is not!
From the electrical view, a GND layer needs to be a low impedance ... thus a GND layer should be solid, without any traces in this layer.
Only if you really know what you do .. you may insert some traces at uncritical areas. .. or split the GND plane.

Low Impedance:
Donīt mix it with "low ohmic".
* low ohmic is a "DC" value. It mainly is the copper resitance between two points. Thicker and wider traces will reduce resitance.
* but "low impedance" is an AC value. (You know that an amplifier does not oscillate with DC frequency ;-) ). Unfortunately wider, or thicker traces, or copper filled areas do not necessarily reduce impedance that much.

Klaus
• 9th November 2019, 20:49
andre_teprom
Re: Ground plane in audio amplifier?
Quote:

if touching the input with the tip of whatever, the amplifier oscillates
it is likely being not self oscillation as you think, but rather a bare injection of EMI ( e.g , from mains ) through your fingers.