Substituting a transistor

[[email protected]]

I am going to trade a BC547 transistor for a TSxxxx transistor (Taiwan
Semiconductors).

In the datasheet of the BC547 I have read the following:

Vcbo=50V
Vces=50V
Vebo=6V
Ic=100mA

I took a look on the website of Taiwan Semiconductors. Here's a nice
overview of their transistors and their V's and Ic:
http://www.ts.com.tw/TSCbig5/front/bin/ptlist.phtml?Category=100084

So I explored the list and tried to find a matching substitutor. But I
notices that sometimes the V's are the same, but then the Ic is too
high. And then when I seem to find a transistor with the correct Ic,
it's the V's are way too high again. In short: there's no perfectly
matching transistor.

Does this mean non-of these transistors can replace my BC547? I read on
this newsgroup that very often any transistor will do. (which doesn't
really make sense imho, since often there are several types of
transistors used in the same circuit). Still I will have to make a
decision. So I guess not all factors are as important and that there
will be a transistor that will be good enough?

My main question is: what is the most important factor of a transistor?
Is it the Ic, Vcbo, Vces or the Vebo. And do my V's and Ic have to be
at least as high of the values of my previous transistor, or should
they only be maximum the same value and not cross it? Or do I just need
to find values as close as possible?

Thank you in advance,
I hope somebody can clear this up for me
BramGo

(In case anybody wonders... It's really more as an experiment I am
substituting the transistor.)

 

[John Popelish]

I am going to trade a BC547 transistor for a TSxxxx transistor (Taiwan
Semiconductors).

In the datasheet of the BC547 I have read the following:

Vcbo=50V
Vces=50V
Vebo=6V
Ic=100mA

I took a look on the website of Taiwan Semiconductors. Here's a nice
overview of their transistors and their V's and Ic:
http://www.ts.com.tw/TSCbig5/front/bin/ptlist.phtml?Category=100084

So I explored the list and tried to find a matching substitutor. But I
notices that sometimes the V's are the same, but then the Ic is too
high. And then when I seem to find a transistor with the correct Ic,
it's the V's are way too high again. In short: there's no perfectly
matching transistor.

Does this mean non-of these transistors can replace my BC547? I read on
this newsgroup that very often any transistor will do. (which doesn't
really make sense imho, since often there are several types of
transistors used in the same circuit). Still I will have to make a
decision. So I guess not all factors are as important and that there
will be a transistor that will be good enough?

My main question is: what is the most important factor of a transistor?
Is it the Ic, Vcbo, Vces or the Vebo. And do my V's and Ic have to be
at least as high of the values of my previous transistor, or should
they only be maximum the same value and not cross it? Or do I just need
to find values as close as possible?

Thank you in advance,
I hope somebody can clear this up for me
BramGo

(In case anybody wonders... It's really more as an experiment I am
substituting the transistor.)

I am not seeing your specs on the data sheet:
http://bittoum.home.cern.ch/bittoum/datasheet/bc547.pdf

But to get back to your question, many substitutes might be possible,
but to decide what specs must be well matched and which may simple be
exceeded, you need to understand what the transistor is limited by in
the circuit in question. If you want a substitute that will work in
any application, all the specs must be equaled (at least). Besides
collector voltage and current ratings, you might need to consider DC
gain at low current, the current that has the peak gain and the gain
at the current where the gain falls to something like half of the peak
gain. You might have to be concerned with saturation voltage (if
being used in a switching application), and collector to base
capacitance and fT, if speed is a concern. And you might compare
noise figure if that is important (and the two data sheets are at all
similar in their definitions and test conditions).

 

[Chris]

I am going to trade a BC547 transistor for a TSxxxx transistor (Taiwan
Semiconductors).

In the datasheet of the BC547 I have read the following:

Vcbo=50V
Vces=50V
Vebo=6V
Ic=100mA

I took a look on the website of Taiwan Semiconductors. Here's a nice
overview of their transistors and their V's and Ic:
http://www.ts.com.tw/TSCbig5/front/bin/ptlist.phtml?Category=100084

So I explored the list and tried to find a matching substitutor. But I
notices that sometimes the V's are the same, but then the Ic is too
high. And then when I seem to find a transistor with the correct Ic,
it's the V's are way too high again. In short: there's no perfectly
matching transistor.

Does this mean non-of these transistors can replace my BC547? I read on
this newsgroup that very often any transistor will do. (which doesn't
really make sense imho, since often there are several types of
transistors used in the same circuit). Still I will have to make a
decision. So I guess not all factors are as important and that there
will be a transistor that will be good enough?

My main question is: what is the most important factor of a transistor?
Is it the Ic, Vcbo, Vces or the Vebo. And do my V's and Ic have to be
at least as high of the values of my previous transistor, or should
they only be maximum the same value and not cross it? Or do I just need
to find values as close as possible?

Thank you in advance,
I hope somebody can clear this up for me
BramGo

(In case anybody wonders... It's really more as an experiment I am
substituting the transistor.)

Mr. Popelish has given good advice. But I'd like to know why you
didn't provide the exact part number of the transistor you're
replacing.

I'd assume you would probably be able to replace a TSxxxx with a
BCxxxx. ;-)

If you want an almost certainly good substitute, you need to know what
you're substituting. Make sure you equal or exceed all the relevant
specs. And there are many other specs besides working voltage and
maximum current.

But if there are no exact matches, then you have to get a circuit
schematic and work out exactly what the circuit is doing. Figure out
what's important and what's not. For instance, if you're using a
transistor as a slow speed switching relay driver, f(t) probably isn't
going to be too important. Nor are various capacitances. You'd be
more concerned with h(fe), Ic(max), and V(ceo).

Many times, especially with power transistors and high frequency
circuits, there is no good substitute.

Good luck
Chris

 

[Phil Allison]

http://www.ts.com.tw/TSCbig5/front/bin/ptlist.phtml?Category=100084

** Nothing close to a BC547 here - even the pin outs are different.

My main question is: what is the most important factor of a transistor?
Is it the Ic, Vcbo, Vces or the Vebo. And do my V's and Ic have to be
at least as high of the values of my previous transistor, or should
they only be maximum the same value and not cross it? Or do I just need
to find values as close as possible?

** Transistor type number substitution is not a simple exercise.

The very first thing is to get the polarity, package and pin outs the same.

Vce, Ic and Hfe (beta) need to be the same or somewhat higher.

Then check the Ft (gain-bandwidth product) is similar.

Then the power dissipation figure, which can vary greatly even with the same
package.

Some devices are specialised for radio frequency work or switching, so look
at the maker's description to.




......... Phil

 

[Phil Allison]

"Chris"

Mr. Popelish has given good advice. But I'd like to know why you
didn't provide the exact part number of the transistor you're
replacing.

** Huh ???????

The OP mentioned it was a BC547 no less than three times.






......... Phil

 

[Chris]

"Chris"


** Huh ???????

The OP mentioned it was a BC547 no less than three times.






........ Phil

Thanks, Mr. Allison. I read "I am going to trade a BC547 transistor
for a TSxxxx transistor (Taiwan Semiconductors)." and somehow
interpreted that to mean he was replacing a Taiwan Semiconductors
something with a BC547, instead of the other way around.

My mistake. Thanks again for the spot.

Cheers
Chris

 

[[email protected]]

This is very interesting for me. I have a datasheet from "Vishay
Semiconductors"
It shows:
50V,50V,6V,100mA

while your specifications from "Fairchild" show
45V;50V,6V,500mA

and I also found the specifications of "Philips"
45V;50V;??;500mA

I guess I was wrong when I thought I could just download circuits from
the internet, buy the parts and assemble them.
(When even a partnumber can have different meanings) But I'll go with
the 45,50,6,500 as you showed me.

 

[[email protected]]

Thank you for your reply Chris.

Make sure you equal or exceed all the relevant
specs. And there are many other specs besides working voltage and
maximum current.

TS13007CZ:
Vceo = 400V
Vcbo = 700V
Vebo = 9V
Ic = 800mA

I guess this could then replace the

BC547:
Vceo = 45V
Vcbo = 50V
Vebo = 6V
Ic = 500mA

Would this work? (By the way it will probably be used in applications
like a PIC-microcontroller programmer and a USBtoSerialport Converter)

Thank you in advance
BramGo

 

[Phil Allison]

TS13007CZ:

** A TO220 pack device - you fucking moron.

BC547:

** NO - you half witted baboon.




.......... Phil

 

[Chris]

Thank you for your reply Chris.


TS13007CZ:
Vceo = 400V
Vcbo = 700V
Vebo = 9V
Ic = 800mA

I guess this could then replace the

BC547:
Vceo = 45V
Vcbo = 50V
Vebo = 6V
Ic = 500mA

Would this work? (By the way it will probably be used in applications
like a PIC-microcontroller programmer and a USBtoSerialport Converter)

Thank you in advance
BramGo

Hi, BramGo. I'm not sure why you're focused on Taiwan Semiconductor
(unless you work there). There are a couple of problems with your
possible substitution. Both transistors are NPN. However, the
replacement you're suggesting is a much larger TO-220 package. While
it exceeds the BC547 on voltage specs by an order of magnitude, it's a
relatively slow transistor (f(t) = 4MHz). That's going to be an issue
if you're trying to switch voltages at microsecond speeds. It won't
switch as quickly. Also, the pinouts are wrong. Like a lot of power
transistors, the TS13007 has a BCE pinout. That isn't close to the
BC547 -- if you wanted to force it into an existing board, you'd have
to twist around some leads. Also, if you've got an existing board, the
physical board holes for a TO-92 transistor are too small for a TO-220
lead -- it may not fit in the holes.

NPN transistors of the BC547 type are called gumball parts -- they're
commonly manufactured by many sources, and are relatively inexpensive.

The BC547 is a gumball-type part. If you look at the data sheet:

http://www.fairchildsemi.com/ds/BC/BC547.pdf

a couple of things come to mind. First, the NPN transistor part pinout
is a little odd -- the leads on the TO-92 package are backwards from
the standard EBC configuration (looking at the flat part on the front
of the package, with the leads down, reading from left to right). The
BC547 is CBE. If you have a circuit board you're working with, you can
solve this problem by replacing with a more standard transistor, and
putting it in backwards (like the NTE123A mentioned above). If you're
doing a prototype, though, you don't have to worry about it.

The second thing that comes to mind looking at the datasheet is that if
you're using this as a voltage switch at microsecond speeds, you might
be able to do better. This Fairchild data sheet says maximum current
is 100mA, with maximum power dissipation 500mW. Many TO-92 transistors
can switch more current.

On the plus side, the BC547 is optimized for higher voltage gain and
speed at that current.

If I were looking at this, I'd see if your application is using
voltages over 40V (from your description, probably not). I'd then grab
an NPN transistor called the 2N3904 (Vceo = 40V, Ic(max) = 200mA, all
other specs similar) and just put the transistor in the board backwards
if this is a replacement application.

http://www.fairchildsemi.com/ds/2N/2N3904.pdf

Look at the similarities on the datasheets, and see for yourself. By
the way, if you're going to post again, please mention if you're
repairing an existing board, or building something new. Also please
describe more about what your transistor is doing.

Good luck
Chris

 

[JeffM]

I am going to trade a BC547 transistor for a TSxxxx transistor

I took a look on the website of Taiwan Semiconductors.
BramGo (bvandenbon @ gmail.com)

Foley questioned your apparantly arbitrary exclusion
of all but a single source. I do as well.

http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm

http://www.ee.washington.edu/circuit_archive/parts/cross.html

Greg Szekeres apparantly has a cross-reference page, but,
having run it thru the WorldWide Web Consortium's HTML checker,
I have to wonder what horrible Horrible HORRIBLE tool
he used to construct it:
http://validator.w3.org/check?uri=http://www.pitt.edu/~szekeres/shopchip.htm

Here's an old dead-tree variant:
ISBN 0-672-21335-4
http://www.bookfinder4u.com/isbn_search.html

The word "gumball" (aka "jellybean") was also used.
That could be apt.
The more details you provide,
the better the advice you are likely to get.

 

[[email protected]]

Hi again,

Thank you for all your comments.
And thank you for those hyperlinks.

The sequence of pins aren't really that important. I am using a
prototyping board so it's easy to switch some wires.

Electronics is totally new to me to be honest. In september I started
studying Industrial Engineering in the field of Electronics. Normally
it would take 4 year to graduate in it. But I received an adapted
scheme due to my previous studies in the field of Computer Science. So
I am doing the first 3 years in just 1 year. The problem is: most of my
teachers assume I allready had over 2 year experience with the basics
of analog electronics. But I'm actually a total beginner. Next year
I'll have to write a big paper and do a training period in order to
graduate. So in preperation of that I am trying to make up the
experience I don't have.

Choosing transistors is pretty complicated for me. Maybe it would be
easier if I would better understand the circuits. I don't get the exact
meaning of it in certain situations. (I do have a basic knowledge of
what a transistor is: I know it can be used as a kind of amplifier
depending on the current on the base.) But there are certain situations
where I do not understand the importance of it. For example in the
diagram on the following webpage:
http://www.circuitsonline.net/circuits/view/91

It would be nice if somebody could give a little bit of background

 

[Rich Grise]

Thank you for your reply Chris.


TS13007CZ:
Vceo = 400V
Vcbo = 700V
Vebo = 9V
Ic = 800mA

I guess this could then replace the

BC547:
Vceo = 45V
Vcbo = 50V
Vebo = 6V
Ic = 500mA

Would this work? (By the way it will probably be used in applications
like a PIC-microcontroller programmer and a USBtoSerialport Converter)

It would probably "work", depending on your application, but you don't
need anywhere that high of a voltage:

Try an MPSA06:
Vcbo = 90V
Vce0 = 80V
Vebo = 4V <- You'll have to watch your reverse base voltage, but if that's
under control, it should work fine.
Ic = 500 mA
http://www.fairchildsemi.com/ds/MP/MPSA06.pdf

Good Luck!
Rich