We use TL071CP op amps for our ECE lab exercise. Students measure the slew rate by setting up a voltage follower and inputting a 5Vpp square wave starting at 1kHz and then increasing it until the output rise and fall times are noticeably different - usually in the 100's of kHz.
In the past the parts that I have used from TI meet the spec pretty close to 13V/us. But the latest shipment of parts bought directly from the TI store show that the Slew rate is around 0.5V/us. I've checked several of the parts from the latest shipment and they all fail SR spec. There is a different package for the latest shipment. I attached an image: The part on the image at the top with just the dot is from an older purchase and the SR is fine. The part at the bottom with the half moon has a slew rate of 0.5 V/us.
I've contact TI customer support and spent a day with a person who kept telling me that they were possibly counterfeit, even though I kept telling the support person that they were purchased directly from TI. Once i finally found the invoice number, the TI support person believed me and then told me that another group will now be responsible for helping me. That group contacted me and said to investigate this further, they would have to do a FA analysis, which I understand , but they asked me to fill out a ridiculously long form. So while I am waiting for their response to some questions , I thought I would ask here:
1. Is it common that the measured slew rate would be low but other aspects of the TL071CP op amp appear to have normal behavior? i.e. gain for inverting, non-inverting and differential configurations are all correct. The Bode magnitude plots also seem to agree with the specifications for GBP. My input signal magnitudes are much lower (100s of mV pp sinusoidal signals)
2. What would cause an internal failure in slew rate inside the op amp. The internally compensated capacitor not charging correctly?
