Is there a difference between the to92 and to18 style transistors? For instance a 2n2222? Obviously some transistors only come in one style or the other but if I can choose does it make a difference?
the package has very little bearing on the characteristics of the transistor, except for when it comes to heat handling and dissipation.
cheers
Since you mentioned it specifically and I was just looking this same thing up I Found this article. https://www.etechnophiles.com/pn2222-pn2222a-vs-2n2222-2n2222a/ There was a pack of 100 92's for 7$ on Amazon and I was wondering the differences. My experience the ones in the to-92 are around. 50hfe higher vs the to-18, this could just be the batches though.
Main difference is Collector current (continous) which is about +30% for TO-18..
Despite TO-18 metal can heat dissipation ability, power dissipation rating is similar to (or even lower than) TO-92 one (probably due to TO-18 insulating Base..) but the ability of readily availiable TO-18 heatsinks is an asset..
(in some older designs, mainly UHF applications, TO-18 package was used in the way metal can was sodered directly onto PCB..)
hFE differences (if any) estimation should be a "hustle and bustle" procedure due to only the phase of the moon not involved in.. :icon_wink:
short answer is almost always that different manufacturers (esp copies on Amazon and eBay) will have different specs regardless of the package and regardless of datasheet, so unless you're seeking out vintage transistors for a specific tone/mojo (which were literally made differently back in the day), the outside package doesn't matter, especially in stompboxes 99.9% of the time. If you need super specific specs, stick with mouser since you don't need to worry about knockoffs with them and the datasheets will be pretty accurate to the transistors you receive. Stompbox circuits are incredibly forgiving when it comes to BJT transistors, and most of the time any old BJT will at least do the job. Watch your pinouts tho. make sure they match up.
TO-92 replaced TO-18 because they were cheaper to manufacturer. The characteristics were essentially unchanged for similar parts. Like antonis mentioned TO-18 were metal but on the whole power dissipation specs were lower.
I dug up this historical info some time back. Changeover gained momentum in the early 70's (although the idea of plastic packs were much earlier).
https://www.diystompboxes.com/smfforum/index.php?topic=124599.msg1183026#msg1183026
TO-18 and the larger TO-22 packages were preferred for military equipment because the package was hermetically sealed. The bottom of the case was glass and the leads were made of kovar, a nickel/iron alloy that had the same coefficient of expansion as glass. The case would be the same. For most purposes, the leads would be gold-plated since that was thought to eliminate corrosion and make them solderable but in our experience, the gold was porous enough that the kovar rusted underneath the gold. The tinned leads on a TO-92 package generally fared better. Gold-plated leads looked sexy but only in the same sense that an open-cockpit biplane is sexy. It is old technology that has been left behind.
Quote from: m_charles on July 26, 2022, 02:07:43 AM
short answer is almost always that different manufacturers (esp copies on Amazon and eBay) will have different specs regardless of the package and regardless of datasheet, so unless you're seeking out vintage transistors for a specific tone/mojo (which were literally made differently back in the day), the outside package doesn't matter, especially in stompboxes 99.9% of the time. If you need super specific specs, stick with mouser since you don't need to worry about knockoffs with them and the datasheets will be pretty accurate to the transistors you receive. Stompbox circuits are incredibly forgiving when it comes to BJT transistors, and most of the time any old BJT will at least do the job. Watch your pinouts tho. make sure they match up.
I've been wondering about some of that Amazon stuff! Thanx for the reminder about Mouser.