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changing transistor

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brandon.

New Member
ok i have a little circuit here that uses a npn switching transistor. if any of what i say is wrong just let me know i am very much in the learning process.

well anyways here is the circuit that i want ot use

8910-fig11.gif


ok well the 2n3055 is a pain to mount from what i see of it, and mainly i would like something that has a higher wattage rating.

the basic reson for this circuit is to get away from using a 50watt zener.

but anyways what i wanted to ask was will this transistor work in its place. it is just an npn 200w that i found on mouser. and i also like the mounting style of it much more.

https://www.st.com/stonline/books/pdf/docs/13934.pdf

from the limited information i have giving is it possible to know what to look for to know if this transistor will work in place of the 2n3055? if so what is it that i would mainly be looking for and if not what other information woudl be neaded?

nearly all of my limited electronics experince has been with older tube equipment so this is new to me.

thanks if anyone can stear me in the right dirction.

i would like to be able to find out how to chose the correct transistor for my neads and know what to look for. in this type of a circuit.

thanks again:)
 

Grossel

Well-Known Member
Weird rating

In your datasheet, Vbe0 is rated to 6 volts.

Have you considering using another smaller transistor in aditional to get an darlington transistor

(this is short version of the post - the rest was lost due to firefox doesn't remember post data during accidently closing tab) :mad:
 

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brandon.

New Member
yea that is the thing i have no idea what is happening wiht this circuit. well i mean i understand it is alowing me ot use a 1w zener instead of a 50w like i am used to using.

i just want to have a better understanding of this ciricut. and understand it to a point to be able to pick what ever tranister i would ike to use to suit my needs.

is that transistor carrying current to make life easier on that zener? or is it amplifying what that zener is doing?

this is just a simple circuit to obtain a little bias on a tube amplifier to set th zero signal plate current.

the zener that i plan on using in this circuit will be 30v

thanks and sorry i left that out.
 

brandon.

New Member
yea see that is the thing. ok i am needing 30v on bias. and on this amp there is 1.5 amp of current. it will probably never see that but that is the max i would like to have.

that is why i was wondering how i find a transistor that could handle more current and possibly have a better mounting style.
 

brandon.

New Member
that is one other thing that is throwing me off. there is a wattage rating and a current rating.

now on this i am at zero volts coming into zener 30v out. just say 1.5 amp current.

would i get the wattage ratting for the zener itself from 30v*1.5=45watts?

if that is correct would that also work for the transistor.

i'm sure once i get pointed in the right dirction on how to look at this stuff it will fall inplace but i get to over thinking stuff and not looking at it right because i have no background in electronics and get all messed up.

i have a decent understanding of diodes, resistors, ohms law and that sort. basicaly older style circuits for tube gear. but throw in a transistor and its like i'm looking at chineese letters you know.
 

brandon.

New Member
ok well that is making a little more sence. the amperage rating is just a maximum. and that is why they give you a watage rating. as long as you are within the volts and witin the amperage and then keep those two within the wattage. ok i'm getting that part now.
 

audioguru

Well-Known Member
Most Helpful Member
In your datasheet, Vbe0 is rated to 6 volts.
No.
Vebo is rated at 6V max like nearly all silicon transistors. It has avalanche breakdown (like a zener diode) when the emitter-base diode is reverse-biased with more than 6V.
But the emitter-base diode is usually never reverse-biased.
 

brandon.

New Member
could anyone point me to a tutorial that would show a transistor being used in a similar way or maybe one that i could relate to it with a few pointers?
 

audioguru

Well-Known Member
Most Helpful Member
The transistor is simply turned on when the input voltage causes the zener diode to conduct which causes the voltage to be clamped at that voltage. When the input voltage is reduced then the zener diode barely conducts and the transistor keeps the voltage fairly constant.
You don't need a tutorial to see it.
 
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