What is Top of TIP120 connected to ? Emitter, or Collector?

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1

What is Top of TIP120 connected to ? Emitter, or Collector?
I'm failing to see this info in the datasheet.

Secondary question: are all transistors with metal tops connected as well?

Any info appreciated, thanks

2

The "top" is the heat sink tab and on most devices of this type it is connected to the center lead, or in your case, the collector.

3

Due_unto:
The "top" is the heat sink tab and on most devices of this type it is connected to the center lead, or in your case, the collector.

Thank you. I had scrapped a broken mixer of mine, and inside I found a cool heatsink designed for 2 transistors. So I thought I would put it to use and control two separate devices from the two transistors I hooked to the heatsink... NOT! It took me an hour to figure out it had nothing to do with my code :X

Thanks again!

4

Some of the datasheets are strangely silent about that, but I found one at http://www.onsemi.com/pub_link/Collateral/TIP120-D.PDF that makes it clear that it is the collector:

Screenshot from 2016-12-24 14:21:49.png
Screenshot from 2016-12-24 14:21:49.png620×566 71.8 KB

5

Hi,
Some TO-220 case components do have an insulated tab, but they usually state the fact.
SCR and TRIACs can come in insulated and live tabs.

Tom.. :slight_smile:

6

In transistor manufacturing process after die is sliced from Wafer, the die is attached to a lead frame. All transistors will have large collector area. Hence large area, that is collector is die-attached to the lead frame using Lead preform.

7

KevinGulling:
Thank you. I had scrapped a broken mixer of mine, and inside I found a cool heatsink designed for 2 transistors. So I thought I would put it to use and control two separate devices from the two transistors I hooked to the heatsink... NOT! It took me an hour to figure out it had nothing to do with my code :X

Thanks again!

If you want to mount 2 transistors on the same heatsink, you can get mounting kits to prevent the collecters from being in electrical contact with the heatsink (and each other).

8

The figure in the upper right of the first page of the datasheet shows that the collector (#4) is connected to the tab.

9

Thanks all, great answers! [quote author=Nick Gammon link=msg=3054713 date=1482549789]
Some of the datasheets are strangely silent about that, but I found one at http://www.onsemi.com/pub_link/Collateral/TIP120-D.PDF that makes it clear that it is the collector:

[/quote]

Nice I see in this one they actually labeled it with a 4. The other Chinese sheet I had only labeled 1-3.

Thanks everyone for the great answers, I am smarter today than I was yesterday :smiley: Karma all around!

10

KevinGulling:
What is Top of TIP120 connected to ? Emitter, or Collector?
I'm failing to see this info in the datasheet.

Secondary question: are all transistors with metal tops connected as well?

Any info appreciated, thanks

The tab is the centre pin, at least in my experience. As always if in doubt a multimeter
can be used to check out the continuity.