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AD8017 as op-amp follower over heat - current sinking

Question asked by Damien on Aug 15, 2013
Latest reply on Aug 18, 2013 by Damien

Hello There,

 

Having quite some trouble with the AD8017.

 

The first stage is used as an amplification and the second one as a follower, it seem that the follower is sinking 200mA (seem to be limited by over-heat protection) current while the output is connected to a 200ohm resistor, how is that possible ?

 

I cannot trace where the current might go, the only possibility is that it is directly drawn from +Vs to -Vs of the op-amp.

 

Probably I'm missing some piece of information or have a lack of understanding op-amp, or this particular op-amp have specificity ?. I've been through the documentation a couple of time and could not find out the problem.

 

The simulation on Proteus seem to work well without sinking current. Besides that the component over heat and draws current the circuit seem to work.

 

Probing with a 200Mhz oscilloscope did not reveal any oscillations.

 

The schematic is attached. Vin may vary between 0 to 5V and is most of the time in DC.

 

My guess would be that I have a sort of current loop between pin 7 and 6 of the AD8017, as if I short pin 5 and 6, it stops sinking current.

 

Any advice or hint are welcome as I'm quite stuck in that.

 

http://www.analog.com/static/imported-files/data_sheets/AD8017.pdf

 

Edit:

Some interesting behavior, during lunch break the circuit was powered off, when I powered on, it seem that the problem has vanished, while nothing has been touched on the board. Same behavior on two boards.

 

It may happen the pin 2 and 3 may have a small voltage before the chip get its supply, this might cause the chip to go on some particular state

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