Transistor Question

Status
Not open for further replies.
Jump to Latest
Tripmaster

Tripmaster

Member
Joined 2008
#1
Hello

I am currently building the Pedja Rogic’s discrete power supply for my dual mono Chipamp LM3886.

I have assembled the V+ section of the power supply and have started positioning the components for the V-. I have just noticed the component supplier has sent three types of BD140 Transistor.

BD140, BD140-16 and BD140-16R4

Is it ok to use a BD140 and a 16 in the same circuit?

It looks like they are also from three different manufactures.

Thanks for your help

Richard
 
#4
I just called Crinklewood and spoke to Chris who was very helpful 🙂

‘-16’ refers to a plastic back transistor and ‘R4’ is the metal back version.

He also said all of the transistors regardless of make will perform in exactly the same way.
 
#5
Yes, they are basically same transistor.
There can be some variation in HFE, gain.

BD140-16 .. is the most usual, lowest gain class ( ~160 )
BD140-25 .. is a class for those exemplars with higher gain ( ~250 )

BD140 .. only, can be in any gain span, is not classified and marked
with any of the above

Personally I have never seen any marked R4. The metalback.
 
#6
lineup said:
Yes, they are basically same transistor.
There can be some variation in HFE, gain.

BD140-16 .. is the most usual, lowest gain class ( ~160 )
BD140-25 .. is a class for those exemplars with higher gain ( ~250 )

BD140 .. only, can be in any gain span, is not classified and marked
with any of the above

Personally I have never seen any marked R4. The metalback.
Click to expand...

Thanks for the info.

Would you recommend I change them all to the same type?

Richard
 
#7
hello all to you.
the number behind the bd 140 - designation is the hfe-classifikation,there are some from 6,10,16,..............the bigger number means the greater hfe-value.
what hfe - (minimum )value you need depends on your circuit design..........
greetings.........
 
#8
mjf said:
hello all to you.
the number behind the bd 140 - designation is the hfe-classifikation,there are some from 6,10,16,..............the bigger number means the greater hfe-value.
what hfe - (minimum )value you need depends on your circuit design..........
greetings.........
Click to expand...


Hello again

I am building the power supply schematic at the bottom of this page

Discrete Regulated

http://myweb.tiscali.co.uk/nuukspot/decdun/prp/supplies.htm

Richard
 
#9
hello.
the schematic with the three-transistor-darlington?- i think this will give you enough current amplifikation (high hfe - value......).
but perhaps there will be a little problem with the heat-dissipation with loud music,i did not calculate it but i think yuo will need big heatsinks........
greetings.........
 
#10
mjf said:
hello.
the schematic with the three-transistor-darlington?- i think this will give you enough current amplifikation (high hfe - value......).
but perhaps there will be a little problem with the heat-dissipation with loud music,i did not calculate it but i think yuo will need big heatsinks........
greetings.........
Click to expand...


So just to recap, can I use a BD140 and a BD140-16 side-by-side in the V- supply?


I was going to make some heat sinks like the ones in Nuuks picture.
 

Attachments

  • pedja_reg3.jpg
    pedja_reg3.jpg
    42 KB · Views: 335
#11
No problems.
Like told.
Any variant BD140 will do well 🙂

When you use one aluminum piece heatsink per transistor, there can be no shortcut.
Even if using no TO-126 transistor insulators.
Just do not let those heatsinks come into electrical contact.

If you use eletrical insulators for mount transistors, then is no issue.
Can not be shortcuts whatever.
 
#13
lineup said:
No problems.
Like told.
Any variant BD140 will do well 🙂

When you use one aluminum piece heatsink per transistor, there can be no shortcut.
Even if using no TO-126 transistor insulators.
Just do not let those heatsinks come into electrical contact.

If you use eletrical insulators for mount transistors, then is no issue.
Can not be shortcuts whatever.
Click to expand...


mjf said:
hello.
yes,you can use bd140 ,.............;
I think the heatsinks are too small,they will run hot.be carefull when you power up..........
greetings..............
Click to expand...


Thanks guys 🙂

Crikey those transistors must get hot! Nuuk's used quite a lot of metal on his heat sinks. There must be about 9mm attached to the back of those transistors, and that's not including the bracket to both sides.

Richard
 
#15
Crikey those transistors must get hot! Nuuk's used quite a lot of metal on his heat sinks. There must be about 9mm attached to the back of those transistors, and that's not including the bracket to both sides.
Click to expand...

No they don't get hot at all. But Pedja told me to heatsink them and that's what I made up from scraps of aluminium lying around the bench. 😉
 
#17
AndrewT said:
Hi,
measure the voltage drop across the pass transistor.
Measure the current through the pass transistor.
Multiply Volts * Amps to arrive at Watts. Choose a heatsink to suit.
Click to expand...


Thanks Andrew

I will do what you suggest just so I understand. I'm sure Nick's are just fine or he would have changed them.

Richard
 
#20
Hi Andrew

What is the formula to calculate the LM3886 power output? I will be using 2x300va transformers with 25v secondaires. Pedja's discrete PS has a dc output of about 26-27v. I am wondering if there will be enough power to drive my 8ohm 88db speakers.

I currently using an unregulated snubberized power supply, this is more than adequate.

Thanks again

Richard
 
Status
Not open for further replies.
Top Bottom