Originally posted by peter@siemens in the EngineerZone feedback forum (before the Amplifier forum was live).
We are trying to build avoltage to current output stage for a new product with the above device. Input -5v to +5v required output current -12.5mA to +12.5mA
A colleague built a prototype unit based on the circuit in the data sheet and the performance was very good. I laid out a board using SOIC devices and the +ve performance was good but the -ve would only remain stable to about 12.3mA after that, if set to 12.5, it would slowly decay on what appears to be a temerature related factor as cooling the device restores the output. I laid out a further board for PDIP parts and tested these - again, negative output decays.
The gain pins on the device are Open Circuit giving a gain of 1 and the input scaling resistors are pretty low - 2k7 in series and 1k shunt.
One theory I had - the input comes into pin 3 (non inverting) - Pin 2 is grounded - should this go via a series resistor or shouldn't that make any difference?
When I used the device from my colleagues prototype, it worked fine - swap back and the problem is still there.
Do you have any thoughts?