accuracy of BCV62

Have you seen diodes matched pnpn's?

All diodes matched pairs

The test circuits, fig 2 and 3, don't make sense.

And transistors are "Q" not "TR".

Emitter resistors will improve mirror accuracy.

Horrible data sheet.

Are these monolithic? Fig 4 looks like some sort of thermal runaway limit, so they're probably not.

Here's a UPA800 dual transistor, thermal image with one transistor dissipating 80 mW. The other transistor is nowhere near the same temp.

ftp://jjlarkin.lmi.net/UPA800_80mW_one-side.jpg

Such "dual" transistors aren't a lot better than two separate beta-graded transistors.

John

From thier website.

"Built with adjacent die from a single wafer: DC Current Gain, hFE, VCE(sat), VBE(sat) are matched to a 2% maximum tolerance."

Which is better then the BCV62.

If the thermal situation is poor, as it almost always is for separate die, the Vbe matching is only good at very low currents.

John

Those are isolated dice--meaning you have to keep the dissipation way, way down to avoid nasty offsets and drifts. A 1 degree C temperature difference--say 3 mW differential dissipation--will give you a 9% I_C mismatch.

Monolithics are much better.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal

I didnt know it was that bad.

It's usually better but they do not guarantee it. Not sure if they'd mix devices from different wafers but that can make for a huge difference.

If you need closer tolerance straight out of the gate it'll be a lot more expensive:

--
Regards, Joerg

http://www.analogconsultants.com/

The lack of promised accuracy was annoying but I can deal with it. Temperature is another matter. In all the threads I've seen here about current mirrors and dual transistors, nobody was ever able to tell for sure whether the parts were built on a single die. It would be nice if somebody did some more testing of various parts, like that infra-red photo John Larkin just posted. God forbid they should tell you anything useful on the datasheet.

It's not that hard to figure out. For instance, check out Fig 4 of the BCV61 datasheet--it shows that for zero emitter resistors, a 1 mA collector current gives you 30% error (about 7 mV Vos or 3.5 C) with Vce=9V (9 mW) and a 5 mA does the same at about 3V. Either way, it's ballpark 200-300 K/W, which is way too high for a monolithic--it's comparable to the theta_jc of the package.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal

Datasheets are nowadays rather dumbed-down, don't expect much. What does help (mostly ...) is contacting application engineering. I know this will dash some of your hopes but the typical dual-transistor is not on a single die. It's multi-chip. Else you'd have entries for voltage differences or substrate breakdown in the abs max ratings.

There are very few true arrays left. In the CMOS area you still have the cheap CD4007, in the upper class the SD5400 series but that has gone boutique, meaning higher cost. AFAIR National took over the CA3046 monolithic array from RCA if you can redesign for NPN:

... and Newark has stock:

Sometimes "re-purposing" chips like the MC1496 works but that depends on what exactly you want to do:

These guys at least assure you that they only use devices from the same wafer:

Hope this helps.

--
Regards, Joerg

http://www.analogconsultants.com/

So if I can run 1mW that gives ballpark 500uV offset, or 2% current error. Thanks, that helps.

The information is usually somewhere in the datasheet. It may take some interpretation, though. You can also call an FAE.

I just killed an Infineon BCV62C just to watch it's die.

It is definitely 2 chips. Thermal coupling should be _much_ better than two TO-x glued together, but the one with the wide leg enjoys much better cooling.

regards, Gerhard.

cooling.

Thanks very much for the effect. I think Phil Hobbs' logic nailed it for me already, though. It was exactly the right way to look at the datasheet and immediately made total sense when he said it. You went out and found what theory said must be true. Reminds me of Dave and the resistor grid! ;)

Jon

In Reno?

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."

I hear the train a comin' It's rollin' 'round the bend, And I ain't seen the sunshine, Since, I don't know when, I'm stuck in Folsom Prison, And time keeps draggin' on, But that train keeps a-rollin', On down to San Antone.

When I was just a baby, My Mama told me, "Son, Always be a good boy, Don't ever play with guns," But I shot a man in Reno, Just to watch him die, When I hear that whistle blowin', I hang my head and cry.

I bet there's rich folks eatin', In a fancy dining car, They're probably drinkin' coffee, And smokin' big cigars, But I know I had it comin', I know I can't be free, But those people keep a-movin', And that's what tortures me.

Well, if they freed me from this prison, If that railroad train was mine, I bet I'd move out over a little, Farther down the line, Far from Folsom Prison, That's where I want to stay, And I'd let that lonesome whistle, Blow my Blues away.

On a sunny day (Sun, 4 Apr 2010 18:39:29 -0400) it happened "Michael Robinson" wrote in :

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11984 bytes of whitespace, 650 asterisks.

Signifying what?

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."

On a sunny day (Mon, 05 Apr 2010 07:07:46 -0700) it happened Fred Abse wrote in :

Easter egg.