I need a low current zener

On 2 Nov 2006 05:45:39 -0800, Klaus Kragelund wrote in Msg.

A few weeks ago there was a long and detailed thread about this topic:

robert

Robert Latest skrev:

Thanks - that answered my question :-)

Regards

Klaus

Klaus Kragelund a écrit :

Does your shunt ref has to supply varying current or not? Or do you mean that the supply you ref is derived from changes a lot?

Is you're drawing zero or constant current from your ref, then a single BJT and resistor will do the trick:

VCC + | .-. | | | | '-' | +------. | | | .-. | | | | | | 6K8 | '-' >| | |----+-------> ref /| | | | | z === A 5V6 GND | | === GND

You can also use some bandgap ref. which will bring you more accuracy. TLV431 start at 80uA and LM385 adj start at 10uA.

LM4040/4041 series.

John

Hello Klaus,

Short answer: No. I have tried quite hard a while ago and it turns out that the typical "low current zener" is really a normal zener with a gussied up data sheet. As you have already seen that means they are operated in their knee and are thus mushy. Plus sooner or later you'll find yourself in a line-stop situation because a batch ran out of tolerance. One of my clients did :-(

If you can stomach a few cents more per unit consider what Fred had suggested: The TLV431 which is also multi-sourced. I have redesigned several products from zener to TLV and there was never again a problem with those.

Analog Devices came up with some low-current FET based references a few years ago

They seems to have stocks of the ADR291GRZ at a couple of bucks each.