Zener Diode Current Source

How would I make a Zener diode current source? Something like this?

I don't know how to figure out what resistors/transistors/diodes I need.

I guess what I'm asking is, how do I calculate what resistors I need, and the rating for the transistor and the diode (I don't know how to tell if the circuit will burn them out).

Edit: I want the load to receive 1 Amp, the resistance of the load is 0.97232Ω, and I am supplying the circuit with either 8.4V, or 9.6V probably 9.6V.

What I'm looking for, is a set of equations to find values for the resistors. I(believe) I can assume that nothing in the circuit will experience current more than my target current of 1Amp? If that's true, I can get parts rated 1.5-2 times my target current.

Schematic of the circuit I want.

^{simulate this circuit – Schematic created using CircuitLab}

Answer

With an 8.4 volt supply producing 1 amp to supply your load of 0.97232Ω you need to have a total resistance of 8.4 ohms (ohms law is still cool).

As you have only 0.97232Ω you need to put 7.42768 ohms in series.

That will produce 1 amp thru your load. It will also dissipate 7.42768 watts so choose a resistor that is rated for the power.

If, for whatever reason it must be a transistor current source and you need the accuracy of exactly 1 amp I wouldn't use the circuit in your question, I'd use an op-amp controlling the emitter voltage of a transistor like (7) in this below: -

The LM317 circuit I feel would also service your needs BUT, at the end of the day, with an 8.4 volt supply, something (usually the transistor) is going to be burning 7.42768 watts so get big components or a heatsink. It can be a BJT so don't worry too much about (7) showing a MOSFET.

Alternatively, use a switch mode current converter powered from the 8.4 volts and let the inductor and capacitor do what god made them for - taking energy in at one end (at higher voltage) and spitting it out at the other (but at lower voltage).

Smallprint - L and C can do the reverse too and I don't really believe in god, but it sounded cool to say that he invented L and C!