Constant-current LEDs?

0.5 to 2.0 Larkins?

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

rs say it is obsolete and unavailable...

or

an

use

a positive VGS, the output characteristic showing over 5mA at VGS 1.0V for the 1.6mA IDSS part. How come you don't make use of that feature in your Ap ril Fool's circuits...

pletion FET with MIN IDSS in excess of your current source.

The bss126 costs the same as LND150...

PG

D white paper, sing cheapest crap I cold find on Mouser. The bss126 is a 60

0V part IDSS min 7mA and -2.7

Still need a 0.1u input bypass- don't cheat.

;)

Cheers

Phil Hobbs

I didn't know that Sloman knew SI units...

You're right, that was silly. This is better:

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Think so? We'd have to try it.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

liers say it is obsolete and unavailable...

L for

the

dss

e

u can

er use

th a positive VGS, the output characteristic showing over 5mA at VGS 1.0V f or the 1.6mA IDSS part. How come you don't make use of that feature in your April Fool's circuits...

depletion FET with MIN IDSS in excess of your current source.

1.JPG

ALD white paper, sing cheapest crap I cold find on Mouser. The bss126 is a 600V part IDSS min 7mA and -2.7 >

me I'm not seeing...

The thread is quite long now and I have not read all posts at all.

But, it was about driving 4 LEDs, same current, right?

So, a 4017 decade counter with VDD connected to a current source, wouldn't that be simple enough?

Current is applied in multiplexed way to the 4 LEDs. More LEDs can be added if it wont flicker to much (maybe a parallel cap across the LEDs for the a pplication with more LEDs?)

Cheers

Klaus

In your case it would be - in general. Being described as being nearly as much of an ego-maniac as a notorious ego-maniac would worry anybody cleverer than you.

Or - from a more realistic point of view - still just as dedicated to flattering self-delusion.

--
Bill Sloman, Sydney

4V.

An advantage of the discrete circuit is ruggedness--it'll work to at least

48V input with 40v BJTs, guaranteed, and probably a survive a lot more.

You make a solid point about LDOs, but isn't the LM317L's 1.2v reference voltage an advantage? If I used a 3.3v LDO, the LDO advantage is lost if I have to drop 3.3v across the current-setting resistor.

The LM317 is jelly-bean, which to me is a big plus. I'm from those days when we wouldn't use a sole-sourced part, and just two sources was considered a little shaky. I want stuff I design to last.

Cheers, James Arthur

I did university physics in Australia. Non-SI units were mentioned, but only so you knew what was going on in old and US text books.

By the time I got to the UK, SI units were written into the laws of the land (though carpet still got sold in square feet and square yards) and when I was working in the Netherlands, it was all SI. Mike Terrell is a trifle parochial.

--
Bill Sloman, Sydney

It's the most practical, but the various ideas have been fun.

I could've just used high-wattage resistors for current limiters and told 'em 0.6mA LED current at 12v input (the most common situation) was a volt-meter 'feature,' indicating low input voltage. But besides being cheesy, where's the fun in that?

We're all getting old, but sure it beats the alternative. I like the '317. It's a classy old workhorse.

Cheers, James Arthur

That's a classic.

-+- | .------+ | | [10k] | | |/ +----| | |>. .--' | ^ ZD [120] | | '------+ |

Same number of parts as my OP, though.

Great. Slightly old-timey, but as true as ever. I read it several times before it all clicked. I hope you enjoy it.

Cheers, James Arthur

But you really do not believe that or you would be taking me up on a bet.

So still richer than you.

Dan

Cute! Doesn't really scale to dual/quad op amps, though.

Just as easy to bias a 1.25V reference (TLV431), three 100k/100k dividers, each into an op amp (+), output to LED and a sense resistor to GND for negative feedback. An LM324 drives three LEDs, has an op amp to spare, and logic pulldown of any of the divider taps controls ON/OFF.

*sigh* I'm anticipating a suggestion that the TLV431 should be replaced with an LED...

Couldn't you replace that TLV431 with an LED?

Grins, James Arthur

It's immoral to take money from deluded idiots.

Perhaps, but you don't actually know that, and should have enough sense to realise it.

--
Bill Sloman, Sydney

But I am not a deluded idiot. And since $ 10k is petty cash, it really isn't immoral.

I have enough assets that I am convinced that I am richer than you.

bet.

sn't immoral.

You don't think that you are a deluded idiot, but more objective observers might differ.

Somebody with slightly better cognitive equipment would be aware that the m orality of an action isn't influenced by the amount of money involved. The legal consequences may vary, but the morality is unaffected.

to realise it.

An ill-founded conviction. Until you know how much money I've got, you real ly ought to be confining yourself to claims about probable outcomes, rather than expressing a conviction. You really don't seem to be very bright, so it isn't surprising that the logical basis of that reservation does seem to have gone over your head.

Granting your general level of performance, your assets were probably inves ted with Bernard L. Madoff Investment Securities LLC, and you haven't yet n oticed that he's no longer returning your calls.

--
Bill Sloman, Sydney

There's also the 385 standby- stripped of all accuracy while making worst case looks like so, it's cheap:

Please view in a fixed-width font such as Courier.

. . . CCR3 . | . ---+--- . | | . | | . ----- [240] . | + | | . LM385 | fb|----+ . | - | | . ----- | . | |< . +-----| BC856A-T . | |\ . | | . | --- . [27k] \ / ~ . | --- . | | . ---+--- . | . . . . .