I also suspect "pulse noise" is popcorn noise, which is independent of actual noise figure as its due to defects in the crystal or its surface, not the fundamental properties of the device.
Defects in the crystal structure = a bad transistor. Like a bad 2SC458.
”Woke last night to the sound of thunder” - means you left the stereo on when one of those starts giving you fits.
”Woke last night to the sound of thunder” - means you left the stereo on when one of those starts giving you fits.
We're talking individual atomic sized defects, typically on the surface (which is why buried structures are used for low-noise devices). Individual charges can get stuck on these defects, then get knocked out again, then get stuck again - leading to discrete changes in the local electric field - popcorn noise and flicker noise are mainly due to this sort of thing.
The kind of bad transistor you describe has actually deteriorated somehow.
The kind of bad transistor you describe has actually deteriorated somehow.
Does that explain the reported popcorn noise for the lm4562 opamp? Does Doug Self ever mention this in any of his writings?
A
I think all semiconductors more or less suffer from this problem.
In a particular application, I needed to replace about 10% of the AD797 because of popcorn noise taking the device (measuring instrument) in which it was used out of spec.
I think I have a similar problem with my amp right now, the right channel suffers from some very light crackling noise.
I think all semiconductors more or less suffer from this problem.
In a particular application, I needed to replace about 10% of the AD797 because of popcorn noise taking the device (measuring instrument) in which it was used out of spec.
I think I have a similar problem with my amp right now, the right channel suffers from some very light crackling noise.
We want to build hdam SA with these transistors. Should we parallel them to make 2sc2240 or single 2sc2713 is enough?
The popcorn problem seems to be related to static damage. In future every opamp I handle will be done on my anti-static bench with wrist strap in place. Just tipping them out of the tube and just shoving them in a socket in a general lab environment seems to result in questionable noise. I have tubes of LM4562 that I have taken out for this reason. Replaced them with NE5532A's which seem to be a whole lot less sensitive to the static problem.