My dislike of Transistors...

[schmitt trigger]

Transistors are not ugly. No electronic component is ugly by itself. It all depends how it is arranged and wired in the circuit.

Take a look at the following images. This is a high-end audio amplifier offered by Silicon Chip Magazine in Australia. The amplification stage is all-discrete transistors. It is actually quite beautiful.

https://www.siliconchip.com.au/cms/gallery/article.html?a=101519&i=3

https://www.siliconchip.com.au/cms/gallery/article.html?a=101519&i=5

 

[Hippogriff]

I did not mean to offend transistors - or even fans of transistors. I shall rephrase - transistors are ugly when I use them in my basic circuits. ICs, on the other hand, are not ugly, they are rather neat. Hence my desire to use one of them instead of three resistors and three transistors (if that's going to be possible)... so, if I can simplify things as well, by reducing the number of required overall components then I would be a doubly-happy-puppy.

Surely this is not such a strange objective for me to have? Yet, I kinda get the feeling people think I'm nuts to be even asking this... or diss'ing transistors. Simplification, neatness, component count reduction, hopefully less solder joints... all seem like positives to me... and these things are not that expensive, either, so it's not like I'm being overly prodigal.

Just need to know how to properly proceed without buying loads of different ones to test...

 

[schmitt trigger]

OK, got you, I now understand where you are coming from. By its nature, ICs are easier to arrange neatly and there are fewer joints to solder. I fully agree with you there.

 

[audioguru]

I have used a Weller temperature-controlled soldering iron for as long as I can remember and have never burned a transistor with it.
It is always at the correct temperature for soldering and is not too hot like the cheap soldering irons that over-heat the tinned coating causing it to solder things very poorly. It takes only one second to make a good solder joint with it so nothing over-heats.
I use leaded rosin-core solder.

 

[Hippogriff]

I've just ordered two of ULN2803A, just to give 'em a go... see what happens. Fingers-crossed.

 

[Hero999]

Lol.

My instinctive response to this thread was you hate transistors? Are you retarded?

Then I realised that you don't really hate transistors but the TO-92 package.

You can get MOSFETs that come in a DIL4 package like opto-isolators; would that be better?

I think I have some in my junk box, I'll post the part number and datasheet if you're interested and I can find them?

It sounds like you need to learn how to solder the TO-92 package.

It's fairly easy once you know how.

Form the leads as per the image attached.

Tin the middle lead an corresponding pad on the PCB; you might have to remove excess solder if the hole becomes blocked.

Fit the device, and bend the two outer leads so the device is loosely held in place.

Solder the middle lead only.

Straighten the device up and solder the other leads.

 

[Hippogriff]

Then I realised that you don't really hate transistors but the TO-92 package.

Well, that is much more precise, yes. My thread title probably is misleading.

I'm still going to try this ULN2803A, though - after all, it's interesting too. Anyway, I've soldered enough BC377s now to conclude they're a right pain. Thankfully people pointed me in the right direction with Transistor Arrays or Darlington Arrays... sometimes you just don't know the name of what you're trying to search for, but you're sure that it must exist.

I just think - admit? - that an 18-pin IC is overkill for what I'm currently wanting to do... I'd, ideally, like an IC with only three transistors inside it, oh, and resistors too. However, learning is a journey...

 

[3lectrokid]

You can have a look **broken link removed** or cant you get get transistors in a to-220 package and bend the unit flat so it is a bit like an ic with an even edge for the board to rest while soldering.

 

[Hero999]

I couldn't find them. I think I probably gave them away along with a load of other components.

Anyway, I've found this using Google.
**broken link removed**

Perhaps you can just use DIL MOSFETs instead? Since you only want a switch then a MOSFET is normally better suited and you don't need a resistor, although it's advisable to use a 100R gate resistor.

 

[Hippogriff]

I appreciate this pointer. All I would say is please bear in mind I'm just starting out and, so far, I know about PICs, resistors, transistors and LEDs. That's it! I'm now going to see if I can somehow use a Darlington Array... and I'd not mind checking out MOSFETs too... but, right now, it's a grey-area to me. You're right that I only want a switch. So - a MOSFET is nothing more than a Transistor, is that right? Can I get a multi-packaged MOSFET array too?

Sorry - EDIT - but if a MOSFET is just a Transistor - how come it seems that I could get away without a resistor inbetween the PIC output pin going into the Gate, but with the BC337 transistors I have found that I definitely need a resistor inbetween the PIC output pin going into the Base?

I know you say it's advisable above...

 

[vne147]

I appreciate this pointer. All I would say is please bear in mind I'm just starting out and, so far, I know about PICs, resistors, transistors and LEDs. That's it! I'm now going to see if I can somehow use a Darlington Array... and I'd not mind checking out MOSFETs too... but, right now, it's a grey-area to me. You're right that I only want a switch. So - a MOSFET is nothing more than a Transistor, is that right? Can I get a multi-packaged MOSFET array too?

Sorry - EDIT - but if a MOSFET is just a Transistor - how come it seems that I could get away without a resistor inbetween the PIC output pin going into the Gate, but with the BC337 transistors I have found that I definitely need a resistor inbetween the PIC output pin going into the Base?

I know you say it's advisable above...

A MOSFET IS a transistor. The reason that you don't need a base resistor with a MOSFET while you do need one with a BC337 is because MOSFETs are voltage controlled devices while BJTs like the BC337 are current controlled devices. The FET in MOSFET stands for field effect transistor meaning that it turns on in the presence of an electrical field at its gate (analogous with base for BJT). There is VERY little current flow at the gate so you don't need a current limiting resistor between the gate and the PIC output.

 

[Hippogriff]

That is very helpful. Thank you!

 

[Hippogriff]

An update...

Well,

I am happy. I seem to have confirmed that 3 x 470Ω resistors and 3 x BC337 transistors can easily be replaced by a single 18-pin ULN2803A. The two I ordered arrived today and it only took a few minutes to confirm (although I did pop one of them, and a 12F683 oops!) that there seems to be functional equivalence.

I'm happier using this IC than the resistors and transistors. It's big but it simplifies things and they only cost 50p. I'll still keep my eye out for a smaller thing tho', a ULN2303A would be perfect .

**broken link removed**

EDIT: Looks, to me, like the ULN2003AN might be an ever-so-slightly-smaller suitable substitute for the ULN2803A. Will order some and try. Same resistors, just 7 darlington arrays, rather than 8, and loses 2 pins.

 

[amando96]

hi D,
These are some package transistor arrays.
From what the OP is saying the ULN series would be better for him, ULN2803 for example.

NPN Transistor Arrays - Datasheets, Search, Parameters

Regards

EDIT:
Browse for Products | Farnell United Kingdom

oh, I share his dislike for transistors, I got my hands on one of those ULN(the 2003) really simple, takes up less space.
I will never use "normal" transistors again!

 

[danrogers]

ive got a rgb controller with some beefy mosfets switching the power to the leds. I can drive upto 5A per channel, would that not be a better solution that using lower power trans?

 

[vne147]

oh, I share his dislike for transistors, I got my hands on one of those ULN(the 2003) really simple, takes up less space.
I will never use "normal" transistors again!

Takes up less space!?! Here is a picture I just took of a DIP18 PIC next to a TO-92 BC548.

 

[danrogers]

ignore me, I somehow managed to reply only thinking there were a few posts on the first page!

 

[amando96]

Takes up less space!?! Here is a picture I just took of a DIP18 PIC next to a TO-92 BC548.

i meant if i got the same number of transistors, as the chip has ''channels'' say my uln 2003 has 7 ''channels'' takes up less space than 7 transistors, and it's all in a regular IC footprint.

 

[Hero999]

You can also get a quad - ULN2068B

I've Googled around a bit and I'm surprised I can't find and MOSFET equivalents.

I would've thought there would be a MOSFET replacement now with a much lower on voltage and a high impedance input. Does anyone know if such a beast exists?

 

[Hippogriff]

Takes up less space!?! Here is a picture I just took of a DIP18 PIC next to a TO-92 BC548.

There's no need to get into a "mine is smaller than yours" debate here! I am very pleased with the outcome, considering the other day I didn't even know such a thing existed and - thanks to the Internet - I got all you helpful guys helping me, I ordered two to test, they arrived, they worked and now I've ordered a tube of ULN2003ANs to even further simplify (-2 pins). It's a real result. And my approach - and amando96's - is not anything against transistors 'cos, as we've discussed, these are transistors.

I looked at the ULN2068B too... a quad, I thought, would be much better than 8 or 7 for me, but it's the same size package at the end of the day, and doesn't look as convenient as the ULN2803A (and the ULN2003AN) with its common ground / emitter. If the ULN2003AN works just as sweetly (and I expect it to) then I shall be using this in my circuits for anything above, say, two transistors.