BC327/337 replacements

Status
Not open for further replies.
Jump to Latest
#2
This is a very ordinary transistor but with a bit more current than usual. I doubt though that this is an important parameter.

You can replace these types with almost any transistor but if you explain more where in the design they are I can give you a more precise recommendation.

The "40" suffix means hfe more than 400 which could be tricky to find but it's not for certain that you need this. I have a bunch of BC550C and BC560C which may fit.

C = "40"
 
#3
Hi peranders,


The transistors will be at the output of the ELEKTOR discrete
opamp.

Do u think the BD139/140 is overkill for that?


Udi.
 

Attachments

  • 1.jpg
    1.jpg
    95 KB · Views: 993
#5
peranders said:

337 can take a bit more current but I doubt that this an issue.
Click to expand...


How come the 327/337 can take more current than the
139/140??

327/337 are rated 500ma while the 139/140 are 1500ma..

And if I'm using the 139/140 do u think I'll need to bias them
harder than the 327/337?


Udi.
 
#7
udip said:

How come the 327/337 can take more current than the
139/140??

327/337 are rated 500ma while the 139/140 are 1500ma..

And if I'm using the 139/140 do u think I'll need to bias them
harder than the 327/337?
Click to expand...
.... 500 mA vs. 1500 mA which is more? 🙂

udip said:
And if I'm using the 139/140 do u think I'll need to bias them
harder than the 327/337?
Click to expand...
You can probably have the same bias but the base current will be at least 4 times more so pay attention to this.

I see no problem to use BC550/560 though, 15 mA => 225 mW => not too much
 
#9
peranders said:

I see no problem to use BC550/560 though, 15 mA => 225 mW => not too much
Click to expand...

Forgive me for my ignorance in this area, but shouldn't higher
current capability should be a plus?

If I use the BC550/560 instead of the originals (BC327/337)
than I'll have less output current, am I wrong? so
why using weaker transistor will not cause problems?

Maybe It's my english (that is my second language), but when
u say "can take" a bit more current, you mean more driving capabilities, right?



Udi.
 
#11
Ok..Now I understand. My mistake.
You meant that either the 550 or the 337 will have
no problems biased with 15ma (225mw out of
500mw that BC550 can handle)...


I'm thinking of using a buffer at the output..a discrete one
I guess..

I just wanna make sure that the opamp will stay in class A.


Thanks..

Udi.
 
#13
I have for sale SSM2210 and SSM2220 which are the same as MAT but in DIL package.

You can use BC transistors with pretty good results especially since you have a DC-servo and matching is not totally necessary but it helps a bit to bring down PSRR some which is good when it comes to distortion.

Those MAT's have about 15-20 dB lower noise but this is rather unimportant becasue the nosie will be 0.6-1 uV => 120 dB S/N with those "bad" transistors.
 
Status
Not open for further replies.
Top Bottom