Transistors or resistors in parallel

Hi, I wonder if you can connect more resistors, transistors, or similar things so that a higher current can flow through them

Or if they can be connected in parallel to make it work

Hi,
His question is very vague.
My first answer would be: Yes.
But if I detail your need better, maybe I can answer differently.
Suggest that before posting, read the following topic.

RV mineirin

GOOGLE : Electronics 101

These are fundimental concepts of electronics, you should really read up on the subject(s) rather than asking in a forum like this. While a basic answer COULD be yes, it could also be no, depending on the application.

Resistors and some other passive components can be connected in parallel.

Semiconductor components such as transistors, LEDs, rectifier diodes, etc., not so easily, as other components are usually required to balance the current flows.

Resistors yes.
Transistors no.
FETs yes,
LEDs no.

Diodes no.

Those 'no's become 'yes' if additional components/circuitry are added, as @jremington says.

No they don’t. I have been on many projects in industry where trying to parallel up transistors has been tried and it has always failed.
You are fighting physics and physics always wins.

Not that many, evidently. It's not unusual in power amplifiers:

http://education.lenardaudio.com/en/12_amps_5.html

"Some large power amplifiers use many parallel output transistors"

Which I maintain is a big mistake. There is absolutely no need to do this. You can get more stable results using a bigger single FET or indeed paralleling FETs where physics work for you. And anyway it was probably just two transistors they tried to parallel up.
Is this a case of audiophiles being silly like the gold plated mains connectors?

But the bigger reason is that you do not advise a beginners that this is in any way a desirable thing to do, it is a very bad thing to do from an educational point. Just look at the way the question was asked.

I know engineers are very competitive and they will turn back summersaults through rings to come up with totally obscure situations that prove they are right and some one else is wrong. Don’t fall into that trap. Keep the advice here on this forum good and practical and relevant.

And avoid sweeping generalisations unless flagged as such. :wink:

FET is not a transistor? You don't want to confuse beginners and use wrong terminology. Funny.

Even BJTs may be paralleled if you use a small resistor in the emitter. I did not need to do this but AFAIK it is universally accepted this is a viable solution when you need to use more BJTs in parallel - i.e. for heat dissipation reasons. There are good reasons why this should work, no "fighting physics". Who knows what you did wrong that your designs did not work.

Small LEDs may be paralleled even without current limiting resistor. Example are all the wedding/Christmas LED strings sold on eBay. Again there are good reasons for this to work - you don't care if one LED takes 20% more current than some other, no one will notice.

Mike's significant point is the possibility of thermal runaway. If the (semiconductor - thus transistors, LEDs and diodes) component markedly changes characteristics and specifically in the direction of drawing more of the current share as it heats, then the imbalance will increase - dramatically.

That isn't going to happen with the battery-powered Christmas light chains and where the components are both closely matched and tightly bound to a common heatsink such as the 10W and upward LED lights, then it is workable.

Hey you are at it again technically correct man. But you only illustrate my point about back summersaults. You know as well as I do that a bipolar transistor was called just a transistor for many decades before they used the Field Effect to make transistors. So your pedantic comment is technically correct, but in common usage it is not. You know this very well and you do it on purpose.

I am aware some people say "transistor" but mean "BJT". For me it is hard to determine how common this is because BJTs and FETs are mostly interchangeable. It is common to say "use a transistor for xxx" - I don't know if they mean "use a BJT" or "use a BJT or a FET." From time to time I notice explicit "transistor or FET" which I consider slightly funny. But in fact it is confusing and I believe it should be abandoned. After all FETs are here for decades too and are slowly replacing BJTs.
You claim you want to "Keep the advice here on this forum good and practical and relevant." This implicitly include "unambiguous" IMHO.

In what way? Certainly not the way you drive them, calculate the heat dissipation or put them into saturation. Do you know a BjT is a current driven device and an FET is a voltage driven device? Of course you do.

Maybe it is because you are still new to the subject of electronics and have never done it professionally. But I seem to remember that after posting about 1000 questions you declared yourself an expert and said electronics was easy.

No it is not. If you are having heat dissipation issues then you have not designed it right in the first place. What advantage do you have using a BjT over a FET?.

Wow there is a first time for everything.

You assume too much, I was not involved in the designs of these projects, that was done by cleverer people than me. I just built the stuff and repaired it ad nauseam, until the project was abandoned. Three times at three different establishments. I did tell them in the third that it would not work but the project leader thought he could do it. He couldn't.

We have been through this before. The design of battery powered Christmas Tree lights is not a reliable design and the makers have a vested interest in selling you another set. Seeing these tend to be used for one month in a year then a life time of 12 years is considered acceptable and that it will not affect future sales because people don't expect them to last longer, so they can afford crap designs.

Hi,
Paralleling MOSFETs is quite common in DC to AC power inverters.

Some SMPS also do this.

Tom.... :grinning: :+1: :coffee: :australia:

BJTs and FETs are interchangeable in the sense that what can be done with one type can usually be done with the other. Of course some minor changes in the circuit may be required.

What? Transistors in huge packages with large heat sinks are for loosers only?

Examples of sources who thinks it is OK:
Digikey
All About Circuits
Of course one Grumpy_Mike is enough to disprove the "universally accepted" quantifier but is there someone else? Do you have any explanation why it should not work?

That's unhelpfully pedantic, you can easily parallel transistors using small-value emitter resistors as you know. Many audio amp output stages are done this way.

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