pc motherboard grounds

You da man!

I wish I did. Whether he does or not, would you mind describing it?

This one?

U1 and the p-fet are a slow but precise closed-loop current source. It's cascoded into the fast PNP transistor below, which gives us low output capacitance. R3 allows the PNP emitter to move a bit and reduce Early effect. R4 keeps the PNP from oscillating.

The big DC error becomes the base current of the PNP. RF PNPs tend to have have low betas, so we lose some of our precise current to the base, and that changes with tempearture. So we dump the base current into U2, and the resulting signal (drop across R2) increases the effective reference voltage to the upper current source, increasing the emitter current, almost canceling the base current error.

R2=R1 gets us close enough. The base current cancellation is a positive feedback loop, but the gain is low, basically 1/beta, so it's stable.

Jim is on record as not liking this. He won't say why.

Post the circuit WITH VALUES so it can be checked. Otherwise it's a figment of the Napoleonic runt. ...Jim Thompson

What you are saying is that you can't decide if it will work unless I show all the values. Which means you can't find suitable values yourself. Which meand you can't understand it.

QED.

Hint: all the resistor values can be the same.

to

even

I learned the hard way not to believe in anything without proper part values. Nor do i spice up fragments.

?-)

Poxy hell, you point to your own lack of understanding. That is a = totally inappropriate use of an emitter follower. No wonder you have silly problems, you don't grok electronics at all.

It's not an emitter follower, but it is an "emitter-follower type circuit", namely the emitter does not see a low impedance to ground, but the base does. A base resistor is a good way to prevent VHF oscillations. This the the so-called "base stopper" or, or mosfet amps, "gate stopper" resistor in Olde English.

Don't be a jerk.

I rarely Spice circuits, because I design them to work. If I do Spice something, to tune it or to avoid a lot of algebra, it's only a fragment. I never even try to Spice a whole product.

For really fast stuff, there aren't good enough models to make the sims worth much, especially for RF-type parts.

JT gets all worked up when I post circuit topologies without values. I find that strange. It means that the only way he can evaluate a circuit is by letting Spice do the thinking for him. And he can't plug in reasonable values himself.

So, whatever values I pick will not be the right values? You remain a Napoleonic runt. ...Jim Thompson

Anyone who disagrees with Larkin on a technical level receives ad hominem designation as a jerk, old hen, senile, whatever.

The truth is that Larkin is a Napoleonic runt who can't stand to be technically criticized, and will dream up all kinds of excuses, subterfuge, obfuscation to claim he's right, even when he is obviously wrong. ...Jim Thompson

If you whine about other peoples' circuits but can't post anything decent yourself, you *are* an old hen.

If you can't understand a simple circuit without values you can plug into Spice, your instincts are truly shot.

Come on, post a fast, precise current source for us to kick around. Or be chicken.

You can't pick values that would make this circuit work, because you can't understand it. Spice does all your thinking for you.

For Pete's sake, I told you that all the resistors can be the same, so all you have to do now is start at 1 ohm and Spice your way up, one ohm at a time, until it does work. That's the way you "design" anyhow.

Maybe the unknown value of V+ is what's confusing you. Try 10.

Or post an original circuit yourself. Fat chance!

The sad thing is that you cannot possibly believe that about him, but you do.

He probably knows more than you ever will.

That should be "It reminded me of..."

I remind me of me. Johnny Boy reminds me of a self absorbed, self aggrandized asswipe. You ain't all that, boy. Not by a long shot.

It would be easy for him to prove otherwise.

I do in fact believe it of him. If he can't Spice it, he can't evaluate it.

It's very interesting, especially using the base that way. Ten years ago it would have been the subject of an interesting discussion on SED.

I'm constantly reminded of an argument and a falling out that occurred when I was 11. The bystanders here even take sides more than they did then. I specifically said the 'pimp' comment was over the line but haven't taken sides other than that.

It's build it or Spice it to PROVE it.

I DESIGN more circuits per year than Larkin can even count that high.

Like Joerg, I can't publish my work, it's all proprietary. That's why I say "Come by". You can look over my shoulder, but no print-outs (or cameras :-)

Larkin throws up (literally) his problems on this page, but never shows the final solution (probably because he stole the solution from one of responding posters).

Larkin is indeed a Napoleonic runt. ...Jim Thompson

It's only _claimed_ stable, not proven.

It obviously doesn't meet your linearity requirement.

It occurred precisely _once_. Can you cite the message ID? I can :-)

Larkin doesn't want to drop the issue... he'd have nothing left to assault me with. ...Jim Thompson