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Old 11th June 2013, 09:35 AM   #1
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Default Types of transistors pnp npn?

Are the collector base and emitter on the same output leads? Or is something reversed usually? I'm confused and trying to make a simple rough push pull amplifier doesn't really matter how quality it is if i can just make it i can get going from there..
And is the voltage requirement doubled? I have various power supplys.. a 12 volt. 5 volts and 4.5 volts. all amperage is 1 amps for each DC power supply. is that enough?
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Old 11th June 2013, 10:04 AM   #2
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12 volts at 1 amp is plently to make a small amp.

The leads on transistors all vary so you are best looking at the data sheet for each which will show the pinouts.

This is a good reference, just type the device number into the blank box.
Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view

NPN and PNP are different in their polarity. NPN have the emitter arrow pointing out and PNP have it pointing in.

An NPN always has to have the collector more positive then the emitter for it to work. The PNP must have the emitter more positive than the base.
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Old 11th June 2013, 10:32 AM   #3
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The legs on the actual transistor do not always have the same connections. Some are EBC, some ECB some BCE etc. You should consult the data sheet before soldering the transistor.
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Old 11th June 2013, 10:59 AM   #4
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one transistor has these written on it
K D998 212
other one says this on it
K B778 217
they are obviously a pair but i can't find the data sheet for one or the other can't remember which but i found the datasheet for one of them but not the other one. it never comes up with anything accurately describing anything similar to the first one...
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Old 11th June 2013, 11:13 AM   #5
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2SD998 and 2SB778
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Old 11th June 2013, 11:22 AM   #6
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Here are the two datasheets. Most datasheets are easy enough to find on the internet.
Attached Files
File Type: pdf 2SB778.pdf (51.3 KB, 28 views)
File Type: pdf 2SD998.pdf (185.8 KB, 14 views)
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Old 11th June 2013, 11:43 AM   #7
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THANK YOU.
So Much! I've been looking everywhere for these silly little datasheets XD

Edit: upon further investigation it appears the first datasheet.... again.. isn't what i have in my hands... it doesn't look anything like whats shown in the datasheet
What I have appears to be a pnp and npn audio amplifier transistor set... but the datasheet says otherwise.
Can someone shed some light on this? I honestly don't know if it's correct that somehow i have a strange transistor that can take the appearance of what's in the datasheet as something else?

Last edited by realflow100; 11th June 2013 at 11:50 AM.
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Old 11th June 2013, 01:10 PM   #8
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NPN/PNP explains the type of "parts" that the transistor consists of.

NPN: Negative/positive/negative

PNP: the opposite.

From Wikipedia:
Quote:
NPN

Click the image to open in full size. Click the image to open in full size.
The symbol of an NPN BJT. The symbol is "not pointing in."


NPN is one of the two types of bipolar transistors, consisting of a layer of P-doped semiconductor (the "base") between two N-doped layers. A small current entering the base is amplified to produce a large collector and emitter current. That is, when there is a positive potential difference measured from the emitter of an NPN transistor to its base (i.e., when the base is high relative to the emitter) as well as positive potential difference measured from the base to the collector, the transistor becomes active. In this "on" state, current flows between the collector and emitter of the transistor. Most of the current is carried by electrons moving from emitter to collector as minority carriers in the P-type base region. To allow for greater current and faster operation, most bipolar transistors used today are NPN because electron mobility is higher than hole mobility.
A mnemonic device for the NPN transistor symbol is "not pointing in," based on the arrows in the symbol and the letters in the name.[5]


PNP

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The symbol of a PNP BJT. The symbol "points in proudly."


The other type of BJT is the PNP, consisting of a layer of N-doped semiconductor between two layers of P-doped material. A small current leaving the base is amplified in the collector output. That is, a PNP transistor is "on" when its base is pulled low relative to the emitter.
The arrows in the NPN and PNP transistor symbols are on the emitter legs and point in the direction of the conventional current flow when the device is in forward active mode.
A mnemonic device for the PNP transistor symbol is "pointing in (proudly/permanently)," based on the arrows in the symbol and the letters in the name.
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Old 11th June 2013, 05:41 PM   #9
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KTB778 datasheet and application note, data sheet, circuit, pdf, cross reference | Datasheet Archive
KTD998 datasheet and application note, data sheet, circuit, pdf, cross reference | Datasheet Archive
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Old 11th June 2013, 10:15 PM   #10
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that makes a lot more sense than what was first shown to me.thanks!
And those diagrams show that they Are extremely similar nearly identical! I just need to know which wires go to which lead
if the negative and positive input.. are both base's combined? or is one base hooked to negative input and the other base to positive input? (input signal wires?)
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