Startup Circuit for CMOS current source

Hello Phil,

Hand-tuning sure would be. We used to call that "rubber engineering". But an automatic tuning would be acceptable (done that... a lot ...).

Regards, Joerg

Hello Phil,

Cost. If you have to generate, for example, a PWM and there is already something in the circuit that makes it rather easy to measure the ratio it can be a piece of cake to implement a feedback. It sure beats almost any digital solution in terms of cost.

Regards, Joerg

Hello Jim,

I am not a chip guy but wouldn't it be easy to turn that resistor off via a weak device? Even if start-up can't reliably be detected this shouldn't need a large cap.

Regards, Joerg

Hello Jim,

I despise them as well. Reminds me of those dreaded RC resets that you see in micro controller app notes, occasionally even those of upper class manufacturers. Sensing the correct condition, adding a reasonable time delay to that and then shutting off would be better. But if this whole thing runs off a battery and is turned on via electronic means rather than a switch a transient style could work. As long as the battery is soldered in or its contacts are extremely reliable.

Regards, Joerg

Hello Jim,

As I said I am not the chip expert. So don't hold it against me if this is going to be pure baloney and put down the coffee cup to be prepared for a major ROFL episode. Look at figure 2 in the link to Kevin's site that QQ gave us:

What if a resistor would not go straight to VCC but do so via a pnp? For example if the base of that new pnp was connected to a divider between the collector of QN7 and VCC then that new pnp would turn off once the collector of QN7 comes up.

My exposure to chip design was mostly working out the high voltage areas, the noise critical stuff, and where we just had to violate design rules big time. But always together with a chip expert. The digital portion was all handled by him alone but he did show me some similar cases in there where he had to make sure something started in the correct state, to avoid frying something should a control signal not arrive in due time.

Regards, Joerg

Hello Jim,

That had me puzzled as well. But companies in the UK did use very interesting processes. Unfortunately many of them went under. So I got myself a large stash of those fabulous Plessey monolithic mixers before they also rang the last order bell ;-)

Oh drat. Can't rely on threshold levels for that either, I guess.

I wonder why QQ wants to shut it off, considering that it probably is going to be under a uA where it shouldn't take a substantial toll on the battery. But who knows, maybe it is too much.

Regards, Joerg

Hello Jim,

Just received a very non-vague specification, from my wife, to grout the area that I tiled on the weekend. I thought about contracting it out but after seeing what the tile people before me had done I opted not to. Oh well.

Regards, Joerg

Hello Jim,

Just got done grouting, looking forward to firing up the barbie and having a Shiner's Bock beer from Texas. Then maybe a Merlot with the Tri-tip steak.

You certainly have done your fair share of tiling. It looks like you have also become a mudmeister, assuming you did that shower the classical way.

I could think of something nicer as therapy. But at least I found out that the back pain which always resulted from doing the heavy porcelain work traced back to a magnesium deficiency. Some cheap nutritional supplement, no meds anymore and since almost a year no pain. Even after splitting five cords for the winter(s). None of the docs had figured that out. Hmm...

Cool! Like the bath we did in Germany. I told my wife that since I'd do it myself she could pick whatever materials she'd like. Turkish tiles, sea resort style vanity, etc. And sure enough, right after that we had to move :-(

I do, too, but then there is that honey-do list. I guess you may be done tiling for a while but if your sons or anyone else who reads this runs into a tough issue there is an excellent forum to seek advice:

That and a Home Depot class helped me a lot in learning the 'merican way of tiling, with modified thinset and all that.

Regards, Joerg

I would make a long channel length device with the gate at gnd or vdd depending on the polarity, this is the reference current. Then mirror a fraction of the bias current to a current comparator which is comparing the refernce. The output of the current comparator should power a transistor which will be switched off when the bias current excedds the reference.

I d> Hi,

I'm of the Greek school... I don't know strength of materials all that well... so I overdo it.

...Jim Thompson