Example $6.$

$6\mathrm{.}8$ V Zener regulator.

Specifications:

$10$ V supply, minimum Zener current for regulation $10$

mA$,$ load current can vary between $0$ and $30$ mA$.$

Determine the maximum possible value of

S

R

such that

regulation will occur, and its minimum power rating and that of the Zener.

Answer.

$80$

S

R

$$

rated at $128$

mW$.$ Zener minimum power rating $272$ mW$.$

Exercise.

Determine the Th$$venin model of the circuit looking

out from the Zener terminals when the load current is at its maximum valu