We decided to condense an older design using SM components so that we could squeeze this board into a small area.
Got 20 of these from fairchild. after initial testing of the first one. We found some spurious noise being generated only at fixed levels of operation.
After a little testing, we decided to put a MMBTB2222 in a simple common emitter with resistor load on the collector circuit, using a variable bias, we found at ~ 15 ma of Ice, there was ~ 0.5 vpp erratic oscillation in the area of 100k..150khz depending on where the bias was. below or above this point would then place the transistor back in normal operation once again. Testing with a 2N2222 operated fine, I also found another SMT type 2222 which tested fine.
We'll be looking for another semi vender with this same number, I don't want to buy another batch of this number from fairchild just in case I get the same defects.
Have any of you ever seen strange things like this take place?
P.S. It works fine being used in a saturated switch circuit obviously.