Microprocessor based projects external circuitry

Thread Starter

saleemsm

Joined May 15, 2006
36
The Xtal circuit uses high impedance input buffer made by CMOS. Such
high impedance is easy to pickup noise through capacitive
coupling,

we can reduce it by using low impedance copper path making it
known as guard ring.

We can see this also in the high resistant
non-inverting amplifier built by opamp circuit.


my question is:

1. what is the guard ring that is being talked about?
2. where is it seen in the high resistant non - inv amp in opamp circuit.
 

n9352527

Joined Oct 14, 2005
1,198
Originally posted by saleemsm@May 15 2006, 01:16 PM
The Xtal circuit uses high impedance input buffer made by CMOS. Such
high impedance is easy to pickup noise through capacitive
coupling,

we can reduce it by using low impedance copper path making it
known as guard ring.

We can see this also in the high resistant
non-inverting amplifier built by opamp circuit.


my question is:

1. what is the guard ring that is being talked about?
2. where is it seen in the high resistant non - inv amp in opamp circuit.
[post=17114]Quoted post[/post]​
It's just a pcb track surrounding the high-impedance sensitive node. It is usually kept at the same potential as the sensitive node, or driven at the same potential with low impedance. Thus it would sink the stray currents away from the sensitive node.

An example is, for non-inverting op-amp the guard ring is usually connected to the negative (inverting input) and physically surrounds the positive (non-inverting input)
 

Thread Starter

saleemsm

Joined May 15, 2006
36
Originally posted by n9352527@May 15 2006, 12:25 PM
It's just a pcb track surrounding the high-impedance sensitive node. It is usually kept at the same potential as the sensitive node, or driven at the same potential with low impedance. Thus it would sink the stray currents away from the sensitive node.

An example is, for non-inverting op-amp the guard ring is usually connected to the negative (inverting input) and physically surrounds the positive (non-inverting input)
[post=17120]Quoted post[/post]​

thanks for the answer.

I am starting a project and need help in getting started.
 

n9352527

Joined Oct 14, 2005
1,198
Originally posted by saleemsm@May 16 2006, 08:46 AM
thanks for the answer.

I am starting a project and need help in getting started.
[post=17136]Quoted post[/post]​
If you need further help, just start a new thread and explain what you need. Preferably in details and be specific to maximise the chance of getting answers. Good luck with your project.
 
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