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Old 25th February 2014, 07:56 PM   #161
Struth is offline Struth  Canada
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Location: books at londonpower.com
Hi Guys

For the TO-92, the leads are spaced by 100mil, the copperless space between the pads is 47.5mils.

When inserting the BJT, you angle the device slightly and insert the lead at one end, then the middle then the other end. The leads flex easily and you would never push the body all the way down to the board, so the leads are splayed without effort and the part is very secure.

For TO-126s, their leads are already spaced at 100mils so generally I leave them at that. If I want to position them close to a larger device where it would be convenient to bring a fat trace through the TO-126 foot print, I have a "wide" version of this footprint where the leads are slightly splayed. Same for TO-220.

You also have to remember that the bodies of these parts can be thick. In most cases the air above an adjacent resistor or other low-profile part can take up that slack, but you should accommodate it with at least one variant of the library package for the device.

For example, I have fourteen packages that an NPN, PNP, NMOS or PMOS can be, covering small packages like the Japanese SST (like a TO-92 with the back half cut off), to TO-92s, TO-126, TO-220, TO-247 (16mm wide), TO-264 (20mm wide), with normal spacing and with staggered high-voltage spacing. I build circuits that have to handle 1kV, so the standard TO-220 footprint doesn't work for me especially with fat pads.

In the "slim" package variations where I do want to have a tight spacing, I add E,B,C indications on the top silk screen so I orient the part correctly.

Have fun
Kevin O'Connor
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Last edited by Struth; 25th February 2014 at 07:58 PM.
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Old 26th February 2014, 06:48 PM   #162
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Join Date: Apr 2012
Location: Florida & France
I always have to translate to metric, so on the fly it's not so easy for me to perceive the actual sizes if not in metric units. Now that I looked at this closer, I see what you mean, the TO92s have lead spacing at 50mils, but the TO126/220s double that. So it's not really that much of a stretch to spread the leads on those small signals, it can be done without much trouble.

I am taking good note of your remarks.

Quote:
Originally Posted by Struth View Post
For TO-126s, their leads are already spaced at 100mils so generally I leave them at that. If I want to position them close to a larger device where it would be convenient to bring a fat trace through the TO-126 foot print, I have a "wide" version of this footprint where the leads are slightly splayed. Same for TO-220.

In the "slim" package variations where I do want to have a tight spacing, I add E,B,C indications on the top silk screen so I orient the part correctly.
Would you mind sharing some of your eagle parts library? Yours must be done right, which would certainly be better than the ones I am making.
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Old 9th March 2014, 03:44 PM   #163
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Join Date: Apr 2012
Location: Florida & France
I've been looking at various options possible to prevent overloads from over driving signals.

I am looking at multiplying the protections and eliminate the vi limiters entirely.

Even if the amp has been made to keep a "good" behavior when clipping, I want to insert a kind of limiter or compressor ahead of the amp, to keep its clipping to a minimum and absolutely prevent any hard clipping. Only slight temporary clipping must be allowed, which at small levels would hopefully not do any harm to speakers.

Among the options that I've been looking at, are the ones used by carver, crown, crest, etc...

And also this one:

http://rupertneve.com/products/portico-5043/

This is a separate device that is inserted before the amp, and it has its own cost, plus the extra cabling to hook it up of course.

This would be a little more than I am looking for and as a diyer, I'd rather build my own and build it in the amp itself. So I'll be looking at all the options that I can find and hopefully come up with something that I can simulate and then build.
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Old 9th March 2014, 03:54 PM   #164
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Cordell and Jung and Marsh and A N Other have commented on measuring very low distortion levels.
AP and other make equipment designed to measure very low levels of distortion.
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