Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Issue with simple buffer design

Status
Not open for further replies.
U

umesh49

Full Member level 4
Joined
May 29, 2006
Messages
218
Helped
25
Reputation
50
Reaction score
21
Trophy points
1,298
Location
Detroit USA
Activity points
2,633
Hi,
I had implemented a buffer using op-amp OPA171AQDBVRQ1. This is simplest buffer with input at + and – is shorted the output.
It works good, except at few points it shows a jump of few millivolts. This small error even gets 3 times more at more than 100C ambient temperature.
Output was op-amp was not having any load/capacitor at output while doing the measurement using multimeter.
I am attaching here the output profile with input voltage.
Please let me know if any one came across such issue.
Thanks in advance for your help.

Regards,
Umesh
 

Attachments

  • buffer_error.JPG
    buffer_error.JPG
    57.1 KB · Views: 67

I am using high end multimeter which can measure up to 4 decimal digits. I verified the input voltage, it was coming from the DAC output and was having no issue.
 

Maybe your multimeter was changing ranges at around 2.0V which caused the sudden drop in its output voltage.
Maybe the DAC voltage source causes the problem at around 2.0V.
 

it is pop noise. You need to choose a pop noise free buffer if you really care
 

kwkam said:
it is pop noise. You need to choose a pop noise free buffer if you really care
Click to expand...

Hi Kwkam;
Thanks, this is something new I am hearing first time.
Is the POP noise is something which appears consistently at same input voltage? Where in the data sheet they define these characteristics.

Regards,
Umesh
 

THe noise you show is repetitive with X axis DAC output, so I wonder if there is any ground shift spike from the DAC inputs going from ...01111 to ...10000 . If so, this could be digital ground current getting into Analog ground reference for DAC.

I've seen this on ADC's before but not DACs.
 

SunnySkyguy said:
THe noise you show is repetitive with X axis DAC output, so I wonder if there is any ground shift spike from the DAC inputs going from ...01111 to ...10000 . If so, this could be digital ground current getting into Analog ground reference for DAC.

I've seen this on ADC's before but not DACs.
Click to expand...

Hi,
Thanks for your reply. I had verified with ground and everything seems to be alright. It seems to be op-amp is doing something. I observed different magnitude of noise in different boards so it changes from part to part but noise happens around same input voltage always. I am thinking if it has something to do with the way op-amp works. bias point etc.

Regards,
Umesh
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top