AnsweredAssumed Answered

Magic 15V on output pin B AD8599 and AD4075

Question asked by gr4eme on Feb 28, 2014
Latest reply on Feb 28, 2014 by gr4eme

Hi Guys,


This one has me totally confused. I have a circuit designed in house by AD for a project I'm working on as an input stage for my ADC-DSP section.


The problem i have is that the circuits not functioning and even more frustrating is a 15V dc voltage that appears form no where.


I have tested the board and the pad has no DC voltage at all yet as soon as the op amp is soldered in place BAM 15v even removing all caps and resistors on section B I'm still seeing 15v


HELP I'm begginign to loose patience and i really need to figure out whats going on.


I have attached a screen grab of the tracking, the original AD supplied schematic and my version used to gee rate the board. The correct chip is the 8599 but in desperation i have swapped in a 4075 and i still have the same problem


Many thanks