HA17431 Series

REJ03D0678-0300 Rev.3.00 Apr 03, 2007

Page 12 of 19

Application Examples

As shown in the figure on the right, this IC operates as an inverting amplifier, with the REF pin as input pin. The open-

loop voltage gain is given by the reciprocal of “reference voltage deviation by cathode voltage change” in the electrical

specifications, and is approximately 50 to 60 dB. The REF pin has a high input impedance, with an input current Iref of

3.8

µA Typ (V version: Iref = 2 µA Typ). The output impedance of the output pin K (cathode) is defined as dynamic

such as ground.

K

OUT

A

REF

≅ 2.5V

–

+

Figure 1 Operation Diagram

Application Hints

No.

Application Example

Description

1

Reference voltage generation circuit

K

R

Vout

GND

Vin

GND

REF

A

This is the simplest reference voltage circuit. The value of the

Output is fixed at Vout

≅ 2.5 V.

in normal applications.

2

Variable output shunt regulator circuit

K

R

Vout

GND

Vin

GND

A

REF

Iref

This is circuit 1 above with variable output provided.

Vout

≅ 2.5 V ×

Here,

Since the reference input current Iref = 3.8

µA Typ (V version: Iref =

2

the resultant voltage drop to be ignored.