DC Power supply

DC Vout

RL

AC ~110V ±10% 60 Hz

DC out

RL

AC ~110V ±10% 60 Hz

?

VZ

Vin

RS

Zener diode shunt voltage regulator

Vout = VZ

I = (Vin-Vz) /Rs

Example:

Vin = 12 V

Vz = 6 V

I = 1 A

W = 12 w

Drawbacks:

• Heat

• Vz fixed

I Vout = VZ – 0.6 V

I max = *I

VZ

Vin

RS

Ib

Add an emitter follower

VZ

Vin

RS

I

Ib

A convention

Vin

RS

I

Adjustable Vout

R1

R3

R4

+VinVout

Vout =R3 + R4

R4

VBE

Using feedback

R1

R3

R4

+VinVout

Vout =R3 + R4

R4

(VBE + Vz)Improvement

+VinVoutR4

Current limiting

R1

VZ

R2

R3

+Vin

Vout =R2 + R3

R3

VZ Using an op. amp.

LM78 XXV+ in 2

3

Available XX :

05, 08, 09, 10, 12, 15, 18, 24 (V), and etc.

1

V- in LM79 XX V- out

LM117/317Vin Vout

A review of JFET

p

n p

np n

Transistors

MOSFET

+

+

-

-

-

n

-

+

+

+

+

+

+

n-SiAl

SiO2

D

S

G

Transistors

R1

R3

R4

+Vin

Vout

Vout =R3 + R4

R4

VBE