Voltage regulation circuit schematics

AN3399

6/24

Doc ID 018824 Rev 2

1.2

Regulation with external NPN without current limitation

The Figure 2 is the modified circuit of external voltage regulation circuit with external NPN

transistor.

Figure 2.

Voltage regulation with external NPN

The advantage of this circuit is fewer amounts of external components. However this is

Parameters of circuit at Figure 2 are:

●

Output voltage = 5.0 V

●

Output current from 0 to 1 A – (no limitation)

●

As in previous case the output voltage is possible set by change of R1 and R2 value. In case

of R3 = R4 the U3 is possible express from equation:

U

3

U

5V1

R

4

R

3

R

4

+

---------------------





R

1

R

2

+

R

2

--------------------- V



=