LM323, A

6

MOTOROLA ANALOG IC DEVICE DATA

Figure 13. Current Regulator

Figure 14. Adjustable Output Regulator

Figure 15. Current Boost Regulator

Figure 16. Current Boost with

Short Circuit Protection

5.0 V

R

Input

0.33

µF

LM323, A

R

IO

The LM323,A regulator can also be used as a current source when

connected as above. Resistor R determines the current as follows:

IO =

+ IB

∆IB ^ 0.7 mA over line, load and temperature changes

IB ^ 3.5 mA

For example, a 2.0 A current source would require R to be a 2.5

Ω,

15 W resistor and the output voltage compliance would be the input

voltage less 7.5 V.

Constant

Current to

Grounded Load

Input

Output

1.0k

4

6

7

2

3

–

+

0.1

µF

10k

MC1741

VO, 8.0 V to 20 V

The addition of an operational amplifier allows adjustment to higher or

intermediate values while retaining regulation characteristics. The

minimum voltage obtainable with this arrangement is 3.0 V greater

than the regulator voltage.

LM323, A

0.33

µF

R

0.1

µF

Output

1.0

µF

The LM323, A series can be current boosted with a PNP transistor. The

2N4398 provides current to 15 A. Resistor R in conjuction with the VBE of

the PNP determines when the pass transistor begins conducting; this

circuit is not short circuit proof. Input–output differential voltage

minimum is increased by the VBE of the pass transistor.

2N4398 or Equiv

LM323, A

LM323, A

Input

Rsc

2N4398

or Equiv.

Output

R

MJ2955

or Equiv.

1.0

µF

The circuit of Figure 16 can be modified to provide supply protection

against short circuits by adding a short circuit sense resistor, RSC, and

an additional PNP transistor. The current sensing PNP must be able to

handle the short circuit current of the three–terminal regulator.

Therefore, an 8.0 A power transistor is specified.

Vin – VO ≥ 2.5 V