[sdiy] Guard Rings

[David Ingebretsen]

Hi all,

I'm still progressing and working on the Steiner Synthasystem.

I have a question. I am laying out the Dual Sample & Hold/Random Voltage
module schematic here:

http://www.xmission.com/~dingebre/SP_Samp_Hold_1.0.pdf

A current PCB layout closeup showing the guard ring such as it is, is here:

http://www.xmission.com/~dingebre/PCB_part.jpg

In conversations with Nyle, he recommends putting a guard ring around the
high impedance sections and tying it to the output of the voltage follower,
but I'm struggling trying to figure out what these are.

I've decided it should include the nodes/pads which connect to the two FETs
including a couple of resistor pads and the one capacitor pad.

The ring shows as a red line tracing close to the pads of the FETs, cap,
resistor, etc. The guard ring is a trace on both sides of the PCB. It starts
and ends on the emitter of the voltage follower which (I think) is Q9. I
excluded any pads going to ground or power.

First question, is this correct? I put a dashed line around the pads I'm
including in the ring on the schematic.

Second, I've read somewhat about guard rings but would love a link to other
information so I can understand this so I make an intelligent PCB.

Thanks everyone.

David