7809 vs 9.1v zener?

Because the 7809 will give you better regulation and significantly less current wasted to achieve it than the Zener will -- particularly if your current requirements vary. And it's easier to use, once you've verified that you won't burn it up.

A 1N4739A from DigiKey will run you $14.40 if you buy 100 of 'em. An MC78L09 will run $22.00. That's a $0.076 difference, you still have to buy the resistor to make the Zener work, you have to _always_ present it with about 105mA, even when the circuit downstream isn't pulling any current at all, and the regulation won't be nearly as good as the 7809. And if your input voltage varies much then you won't be able to reliably hold the Zener current down enough to use a 1W diode, which means you'll have to spend even more.

If you can stand 9.3 to 9.4V, then a 1N5240 is only $7.32/100, a PMBT2222A is only $7.42/100, and a resistor is something like $0.48/100 -- that gives you much better regulation than a Zener alone, about the same or better dropout characteristics than a 7809, and should cost less than a penny more than your bare nekkid Zener, once you buy the resistor to bias that honkin' big thing.

A BCX70J is only 4 cents, and has a huge, bracketed beta!

Better regulation Lower power dissipation Better ripple rejection, probably Lower output impedance.

Otherwise, not really. ;)

Cheers

Phil Hobbs

Simple zeners are cheap in quantity- you can probably get all three parts for 2-3 cents. But a small transistor does not have the power dissipation capacity of a TO220. If you have a 12V input and need 9V at 100mA, that's 420mW at +10% in, which is too much for an SOT-23.

If you're making a Chinese-assembled gewgaw that doesn't have to work over a wide temperature range or for decades, you can stick an 8050 in there and still stay at less than 3 cents, which is probably less than

You can use a 78L09 which is a small 100 ma regulator however, you do need a little head way before that. These types of regulators require a minimum above the regulated output voltage to work. Like 2 volts or more to be on the safe side.

A zener is ok of you can live with the wasted power. you'll find a integrated solution is more stable and uses less power why it's laying around doing nothing. (quiescent current).

Now I like something like this..

It'll handle up to 40 volts in and start at very low voltage. It has its own internal ref 2.5V that you can use with the voltage divider to configure for the voltage you need.

You can use it as a step up, step down, voltage to voltage. etc..

It handles up to 1.5 A on chip and it's cheap!

It's up to you. Most people these days are very conscientious about power usage, especially when it comes to batteries as the supply.

Jamie

This suggests you want a regulated voltage, but presumably don't care about energy waste. So probably mains power, but what needs regulated

NT

Guitar pedal supply -- pedals are supposed to sound better if you run them from separate regulators. Most draw less than