Power supply elementary question

Suppose I have a voltage divider with 2 equal resistors.
Suppose I want to keep the voltage in the node between the resistors constant, no matter the load driven from this node. Is a zenner the only solution? Do zenners have different breakdown voltages that I can exploid ( of course they have but where I can find a list of this)?

Thanks,
D.

I would rather use an opamp-buffer that reads voltage from the resistor devider and acts as a voltage source ..
After this buffer you can connect any load (theoretically) you like and maintain voltage devision from these 2 equal resistors..

A buffer is something that I missed ! Thanks IanP. But tell me: Say I use the zenner. The limitation in load current comes from the zenners resistor? I am trying to understand how I can regulate current and oltage starting from the very basics.

D.

Dkace,
IF you are talking on the resistor between the suppply and the zener. Yes that is mother of that problem.
Now this is slightly not clear, to have a regulated current we have to design a current source. For a regulated voltage I need a voltage source. Correct me if I am wrong or clarify

No not that resistor.
I meant the resistor of the zenner itself. Say I use instead of a second resistor in the dividor a zenner diode of 5.1V or so. What I am trying to understand and configure is that:

Someone says: Ok, you have this voltage dividor, I want to have steady 5.1 V as an output from 24 V dc supply and I want a 1A current to the load.

The question I am trying to answer is :
1. Do I need to know the overall load to configure the dividor? Why?
2. Will the load make the output variable and not steady ? How can I avoid this using only passive components?
3. Which parameter will give me the specified output current? The resistor between zenner and 24V supply? Do I have to know the zenner resistor?

These are my questions for starting the supply. I have some answers but I want to confirm them first.

Thanks,
D.

Regulators with only zener diodes are not very stabile and depend on the diode and load currents.
Much easier is to use a simple, adjustable voltage regulator (can be linear with a heatsink or switchmode ..).
With passive components you will be always struggle .. as higher current causes hgher voltage drop and vice-versa ..

Ian,
my original idea is to construct a voltage regulator from the beggining. Is not a project or something comercial . I am trying to find out all the dificulties I will encounter starting from a simple voltage divider and moving up to a switch mode power supply. That is why I ask all this rookie questions.

So, say I have this voltage dividor with one zenner( We can start uploading schematics at some point, it will be usefull for all ). The question is:
Since I am experiencing voltage variation with the load, what would be the correct compensation ( passive or BJT) to stabilize at the best point the voltage output? What causes these varietions? Is it the shunt resistance ( zenner-load ) ? Any other considerations?
D.

zener is not the only solution u can use op-amp.if u want data sheet then u can use any reference book

You will not achieve any compensation with passive components..
First step, at this stage forget for a while temerature issue, you need to stabilize zenner diode working condition by adding a constant current source (instead of a resistor) to supply this zenner diode with costant current. This will keep you at the same point at the zener characterisitc (Vz v Iz).
Next thing to do will be to use a BJT transistor as a buffer: base to zenner, collector to +V and output = emitter. This will reduced the influence of a load on the zenner current by the β factor of used transistor (Ic≈β*Ib) .. build a circuit like that and try it ..

I think the limitation should be the first resistor (R1) connects to power.

If you need the output has the high power ability you need a small value of R1, so that the zener drops/draw lots of voltage/current.

It causes a fews problems that:

1) very low efficiency
2) bulky parts in circuit (coz' high power)
3) transient response limited by zener charateristics/ or ambient environment
4) weak current supplying also.

so use zener is somewhat good for a 'voltage genreator', not a power supply.
actually, those are in spec while in swtching mode power supply design.