2N2222A complementary is realy 2N2907A ?!?! - Page 1
Forum section: electronics / beginners

author: Axel1973
author_rank: Regular Contributor
timestamp: December 25, 2011, 09:27:57 pm
content: Hi there,today i downloaded a datasheet for the 2n2222A NPN transistor and i got curious about what transistor would be its complementary one. some internet search got me to the 2N2907A which is mentioned as its complementary on many websites...BUT..i figgured that there seem to be DIFFERENT Ic Ratings on this one!The 2N2222a is rated with a max Ic as 0.8A.The 2N2907A is rated with max Ic as 0.6A.HOW COME??Is a complementary not supposed to support the same ratings, just at the opposite polarity ??Thanks for your help!best regardsAxel

author: Simon
author_rank: Unknown
timestamp: December 25, 2011, 10:16:04 pm
content: not sure how it works but I think IRF540 and 9540 are complements (mosfets) but the N channel is 33A and the P chanel one is 23 amps while the N channel has lower full on resistance so well put of balancefor your BJT's gain and base specs are probably what need to be matched

author: Zero999
author_rank: Super Contributor
timestamp: December 25, 2011, 10:20:16 pm
content: P-type devices generally have poorer characteristics to their N-type counterparts.

author: amspire
author_rank: Super Contributor
timestamp: December 26, 2011, 01:37:16 am
content: Since the properties of P-Type and N-Type semiconductor are so different, it is impossible to make geniune totally matching complimentary pairs.So when you see a complimentary pair, they are usually two completely different transistor designs chosen so that they have a similar voltage capability, current rating, current gain, collector to base capacitance and package type. Usually this means the PNP transistor has to be larger then the NPN for the same current capability. Here are some typical chip layouts:The layouts are different, but they are at least in the same type of layout. A small signal low-noise transistor, a RF transistor, a high voltage transistor or a switching transistor all have noticeably different styles of layouts.In many ways, the maximum current rating is not that important as the transistor is performing pretty poorly at that point. The 2N2222A and the 2N2907A would be usually used at 300mA or less and a working voltage of less then 50V, and they are great general purpose transistors in this range.Richard

author: westfw
author_rank: Super Contributor
timestamp: December 27, 2011, 09:56:57 am
content: Huh. Just what does it mean for transistors to be "complimentary", anyway? I mean, even within a particular part number one expects some significant variation in parameters, which you then go on to compensate for by careful circuit design. There have to quite a broad number of transistors that will "complement" the parameters of any particular transistor, if you only want some significant "overlapping but opposite" parameters.

author: amspire
author_rank: Super Contributor
timestamp: December 27, 2011, 12:41:46 pm
content: Back in the days of Germanium transistors, they did actually sell matched complimentary pairs selected to give the best performance in the fairly basic output amplifier stages of transistor radios. We are talking about reducing the 1kHz distortion from 5% down to perhaps 2%. In the 60's, the high price of transistors meant that designs used the absolute minimal transistor count. An example was the Mullard (bought by Philips) AC127 and AC128 1W output transistor pair.But I think for at least the last 40 years, people have been designing amplifiers to use any off the shelf parts. The cost of transistors is no longer a big issue, so you can use as many as you need to avoid any special custom-selected parts in manufacture.So the meaning now of a "complimentary pair" is really a NPN and a PNP transistor pair that have broadly similar specs.Richard.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 27, 2011, 03:47:21 pm
content: Quote from: westfw on December 27, 2011, 09:56:57 amIt means that they are considered suitable for use in a push-pull driver (such as a class AB amplifier output stage). They will generally be lots of devices you could use, but the designated compliments will be suitable choices from the same manufacturer and process generation with similar characteristics. Generally you should be able to pick a complimentary pair and design around the P device.A big advantage of using complimentary pairs is that they are likely to be available together from the same supplier. Picking two random transistors nearly doubles your chances of having one of the parts discontinued or unavailable.

author: Axel1973
author_rank: Regular Contributor
timestamp: December 27, 2011, 04:56:02 pm
content: WOW!Well THANKS TO ALL who replied! There been realy good explainations with it so i just learned something new again.Question SOLVED!best wishesAxel