Tip41 Emitter voltage issue
stamped
Posts: 68
Hi all,
I am building a basic H-Bridge and I have been having some issues with the output voltage of a Tip41 NPN power transistor. I put my H-bridge together and found that the output voltage is always ~5v, when the voltage applied to the collector is 10v. I have no problem switching the emitter "on"·by applying power to the base, but its always ~5v that is output from the emitter. Any ideas why this is so? I thought the Tip41 would output what is applied to the collector. Maybe this is wrong? I am no electrical engineer..
PS: I do not think there are any issues with the Tip41. I tried a fresh one with a simple circuit, 5v on the Base, 9v on the Collector, and the Emitter output ~5v.
I need ~9v from the Emitter.
Any help is appreciated.
I am building a basic H-Bridge and I have been having some issues with the output voltage of a Tip41 NPN power transistor. I put my H-bridge together and found that the output voltage is always ~5v, when the voltage applied to the collector is 10v. I have no problem switching the emitter "on"·by applying power to the base, but its always ~5v that is output from the emitter. Any ideas why this is so? I thought the Tip41 would output what is applied to the collector. Maybe this is wrong? I am no electrical engineer..
PS: I do not think there are any issues with the Tip41. I tried a fresh one with a simple circuit, 5v on the Base, 9v on the Collector, and the Emitter output ~5v.
I need ~9v from the Emitter.
Any help is appreciated.
Comments
These transistors are current driven, not voltage, so I'm a bit concerned when you say you've put 5 volts on the base.
Also, with npn's its usual for the emitter to be tied to 0 volts.
Cheers
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Tom Sisk
http://www.siskconsult.com
·
When I mentioned applying 5v to the base, I was referring to a seperate "experiment" to see if it would output (Emitter) the voltage on the Collector, when it was "switched on". It also output ~5v, and somewhat proved that my H-Bridge was ok.
My understanding was that a power transistor is used to switch on a voltage seperate from the control electronics. Maybe I am way off here, but that is what I thought. But no matter what I do, the emitter is always ~5v.
Generally speaking how would I get the emitter to ouput the same voltage as is on the collector? Even a simple circuit would be helpful here. In my "experiment" (not the H-bridge), I have a couple of volts going to the Base, 10v on the Collector, but the emitter is ~5v. Any newbie mistakes here (apart from the volts on the Base)?
Does it sound like I have something like my ground tying wrong? Such as transistors in the wrong direction (cathode)?
Thanks again. I appreciate you taking the time to respond.
I have a few H-Bridge schematics already. What I was looking for was a very simple schematic showing how to get 10v out of a Tip41. I have seen an H-Bridge like the one you posted (NPN and PNP).
The thing I am searching for is; I have ~10v on the Collector, shouldnt that be enough for it to output 10v on the Emitter? I am out of ideas as to why it is dropping 5v somewhere along the line...
Perhaps this (see attached) is what you're on about?
[noparse][[/noparse]Note -- RLcould be a motor.· Try experimenting with a high-value resistor at first, 10K or more.· RB could be, at this point, 1K or so.]
I will hook this up later today and let you know how I go. My "experiment" circuit was similar and that was getting ~5v. That said "similar" is not close enough, so I will hook this up exactly and see how many volts I get on the Emitter.
Any help is appreciated!
Are you sure the diode is not in backwards ? That would cause a large current to flow through the transistor (assuming it IS an NPN).
Bean.
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"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·
·· One of the most common mistakes I have seen with the TIP41 is that some people connect it like a 2N3904, where the leads are Emitter, Base, Collector.· On the TIP41 though (from left to right) they're Base, Collector, Emitter.· Do you have them wired correctly?
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Chris Savage
Parallax Tech Support
From the schematic (transistor smoke.jpg) I posted do you see any newbie mistakes, because it is smoking the Tip41's?
Edit:·Just tested·switching the direction of the Diode (1N4004) and its still smoking...
Post Edited (stamped) : 10/18/2006 8:12:56 AM GMT
Bean.
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Cheap used 4-digit LED display with driver IC·www.hc4led.com
Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com
"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·
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Chris Savage
Parallax Tech Support