Hi. I have a problem with a design that I made with the AD8420. I proceed to place the schematic diagram to explain more clearly my problem.
Design a transmitter that receives a voltage of 0 to 10V at its input. The output must obtain a current in the range 4mA to 20mA. For this I have used the AD8420 and I have been guided by the application note CN0314, I have followed its indications and the design I have made is the schematic diagram of the image that I placed previously.
The problem I have is that transistor Q5 (ZXT13N50DE6TA) overheats just as soon as I power the circuit with 24V and it happens that the power supply that I use to supply the 24V is placed in a short circuit and does not deliver the 24V. Upon receiving the temperature of each component I found that Q5 is the only one that overheats, so I proceeded to extract this component and verify the operation of the circuit. By feeding the circuit without Q5 present, the power supply is no longer short and delivers the 24V correctly.
I would like to receive your help in this unusual failure and listen to any suggestions to solve the problem.