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Questions tagged [guard]

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2 votes
2 answers
166 views
+200

How are opamp node voltages being set in the following circuit and what is the use of the diode configuration?

I am using a PCB which has the following opamp configuration implemented. It's supposed to be a precision buffer for the source V3. I accidentally connected the source V4 as well and observed strange ...
needbrainscratched's user avatar
6 votes
4 answers
990 views

Implementing guard trace/ring in PCB design for opamp having high impedance input

In the circuit below I am trying to create a "guard ring" for the opamp with high input impedance (~1T Ohm) to avoid femtoampere current leakage. I'd like to ask you guys if I did it right. ...
Phạm Sáng's user avatar
7 votes
3 answers
1k views

Guard line preventing leakage current

I understand that we put a guard line (which is almost at the same potential as the positive voltage) to prevent leakage from positive line to negative line. Is it possible there is a leakage from the ...
user42423's user avatar
  • 365
1 vote
1 answer
228 views

Guard rings for PCB and specific part

Electronics beginner. I am trying to follow the layout recommendations for this part, which is a high PSRR LDO. For the SET pin, one can read the following (P.15): Any leakage paths to or from the ...
UnstableDynamics's user avatar
1 vote
0 answers
423 views

Designing a guard ring for a transimpedance amplifier

I am at that stage of a PCB design where I need some guidance on guard rings. The Application: The application is a photodiode circuitry (using a pin photodiode and transimpedance amplifier.) The ...
LabMat's user avatar
  • 161
6 votes
3 answers
681 views

Opamp Guard Polygon: Only in Top PCB layer or or all layers

I have an opamp circuit as shown below. My board stack up is SIGNAL-GND-POWER-SIGNAL. I am providing a polygon to Guard the trace which is going to non-inverting the input of the opamp. The guard ...
Confused's user avatar
  • 2,593
5 votes
1 answer
447 views

Considerations for PCB guard ring trace for PH probe

Long time lurker first time poster. I have questions regarding PCB guard rings in a pH meter circuit. I know that a typical combination pH electrode has really high output impedance so you want low ...
Andy's user avatar
  • 51
2 votes
1 answer
242 views

How to fix oscillations in cable guard drive?

I am designing a guard drive for a coaxial cable, to drive its shield as a guard for low leakage measurements. After seeing some issues in the sim, I arrived at the following minimum circuit which ...
tobalt's user avatar
  • 22.4k
11 votes
4 answers
3k views

Active guard shielding for instrumentation amplifier

I want to use the the AD8221 amplifier as a conditioner for my load cell. I saw that to reduce noise I can use an "active guard shield driver" between the "REF" of my amplifier and ...
user278935's user avatar
13 votes
4 answers
30k views

Implementing guard trace/ring in PCB design

I have read here and there some articles about pcb guard trace/ring. But none of them discussed how to correctly implent it. What I could find were some pictures and comparison that cant help me at ...
Dumbo's user avatar
  • 3,284