Transistors

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catcat

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My questions about transistors:

1. What's the min voltage a transistor can use?
2. What's the voltage that the transistor will just start to turn on when appliedto its base?
3. can they be used as rf amps
4. what different ampliferrs exist and what are the most common and/or best for various situatins
5. do i need different protection resistors for different operating voltages?
 
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1)There are literaly thousands of transistors available, with operating voltages from several volts to KV.

2)0.6-0.7V for a silicon transistor or 0.3V for a germanium transistor

3) as evandude says, yes

4)there are many amplifiers available, they are all designed around specific operating paramaters such as bandwidth, operating voltage, ouput impedance, input impedance, try searching for amplifiers on google, or use
http://www.discovercircuits.com/list.htm

5)as evandude said you do need different protection resistors for different operating voltages.

hope this helps
 
this is what is says on the packages:

NPN: 3904B, NTE 194, 9011, A6520, 9014
PNP: 3906, 4687 N908, 9015, 9451 N909
 
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I don't know about the other partial part numbers you posted but the 2N3904 NPN transistor and 2N3906 PNP transistor are very common and inexpensive in North America.
Look at their datasheets at www.datasheetarchive.com .
 
I think you need to spend some time reading online information to get an idea for how transistors work, and then spend some time looking at the datasheets for those transistors if you want their specifics.

your question #4 is a very big one; that's the kind of thing you would probably learn over the course of your 3rd year of college. you at least need to be pretty competent about how transistors work in general before you can start to understand the different types of typical transistor amplifiers.
 
I already know how transistors work and what the do and mainly how amps operate.
 
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Hero999 said:
Well you can't know that much or you wouldn't have asked such nubish questions.
Click to expand...

Yes, it's like saying you know how to drive and then turn around and ask "what is a car?"
 
Optikon said:
Yes, it's like saying you know how to drive and then turn around and ask "what is a car?"
Click to expand...
Or he might be a crackerjack vacuum tube guitar amp designer, and never had a reason to look at a transistor.
 
I just dont know the little technical attributes, I do not own a vacuum tube.

I'm also working on a curcuit that can tell between an npn and pnp.
 
catcat said:
I just dont know the little technical attributes, I do not own a vacuum tube.

I'm also working on a curcuit that can tell between an npn and pnp.
Click to expand...

Well, we're just teasing ya.. do you have more specific transistor questions? So you are building a transistor "tester?" There are plenty of reference designs for these. I had one of those once from Radio Shack of all places! It worked for 95% of the parts I ever tried with it. The last time it mis-identified a part, I vowed to never use it again. I hope your design is more reliable than theirs.
 
$10 DVM - Transistor tester..........

Many DVM have build in transistor testers for as little as $10, including shipping. Link; **broken link removed**
So, why build one?

 
Its simple. The led is on means its npn. Its off means its a pnp.
 

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I think your transistor is connected as an emitter-follower. Its base current is nearly the same as its collector and emitter current because the resistors have nearly the same value. Therefore the LED will still light if the transistor has a very low current gain and if the collector is burned out.
Try it like this:
 

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catcat said:
Its simple. The led is on means its npn. Its off means its a pnp.
Click to expand...

Well, your test will not work.

If you get 2 NPN transistors:

#1 transistor leads configuration is C-B-E.
#2 transistor leads configuration is E-C-B

#1 transistor will turn the LED on. So you gonna be happy and be sure #1 transistor is NPN

#2 transistor will NOT turn the led ON. You gonna be happy, as well, but you gonna think that #2 transistor is PNP. (but it's not).
 
What if you insert a broken npn transistor and because the LED does not illuminate you happily assume it is a working pnp, there are some design flaws with this circuit, definately room for improvement.
 
Then n lets think of one that works.

P.S. How do you guys draw such perfecschematics on the computer? The only way I do it is by My image editor's line and freehand tools.
 
catcat said:
Then n lets think of one that works.

P.S. How do you guys draw such perfecschematics on the computer? The only way I do it is by My image editor's line and freehand tools.
Click to expand...

If the transistor works. The problem will be as I described before:
The leads configuration:
E-B-C
E-C-B
B-C-E
B-E-C
C-B-E
C-E-B

Your tester cannot distinguish the base from the emitter or the base from the collector or the emitter from the collector.

You can find various programs for schematic drawing.
Try this one: https://www.smartdraw.com/specials/electrical.asp
 
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There are many schematic drawing programs available, i use livewire by new wave concepts, cost my £15 but it will also simulate circuits so i can test them before i build them (not a very extensive range of components), another program i have started to use is Eagle, it has a wide range of components available, and can do PCB track layouts aswell.

here is the link for Eagle, it's FREE.


here is a link for information about livewire.
https://www.new-wave-concepts.com/products.html
 
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