OP113/OP213/OP413

REV. C

–7–

Supply Splitter Circuit

The OP113 family has excellent frequency response characteris-

tic that makes it an ideal pseudo-ground reference generator as

shown in Figure 6. The OP113 family serves as a voltage fol-

lower buffer. In addition, it drives a large capacitor that serves

as a charge reservoir to minimize transient load changes, as well

as a low impedance output device at high frequencies. The

circuit easily supplies 25 mA load current with good settling

characteristics.

8

1

4

3

2

1/2 OP113

R3

2.5k

C1

0.1 F

R4

100

C2

1 F

R1

5k

R2

5k

+12V

2

OUTPUT

+

Figure 6. False Ground Generator

SoundPort is a registered trademark of Analog Devices, Inc.

Low Noise Voltage Reference

Few reference devices combine low noise and high output drive

capabilities. Figure 7 shows the OP113 family used as a two-

pole active filter that band limits the noise of the 2.500 V refer-

ence. Total noise measures 3

µV p-p.

8

1

4

3

2

1/2 OP113

10 F

C2

10 F

+5V

–

+

OUTPUT

+2.500V

3 V p-p NOISE

+

10k

10k

6

2

+5V

IN

OUT

4

GND

REF43

Figure 7. Low Noise Voltage Reference

+5 V Only Stereo DAC for Multimedia

The OP113 family’s low noise and single supply capability are

ideally suited for stereo DAC audio reproduction or sound

synthesis applications such as multimedia systems. Figure 8

shows an 18-bit stereo DAC output setup that is powered from a

single +5 volt supply. The low noise preserves the 18-bit dynamic

range of the AD1868. For DACs that operate on dual supplies,

the OP113 family can also be powered from the same supplies.

18-BIT

DAC

18-BIT

SERIAL

REG.

18-BIT

SERIAL

REG.

18-BIT

DAC

AGND

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

LL

DL

CK

DR

LR

DGND

VBR

VOR

VOL

VBL

AD1868

8

1

1/2 OP213

LEFT

CHANNEL

OUTPUT

47k

220 F

+ –

100pF

7.68k

7.68k

1/2 OP213

7.68k

7.68k

330pF

9.76k

330pF

9.76k

6

5

7

100pF

RIGHT

CHANNEL

OUTPUT

47k

220 F

+ –

+5V SUPPLY

Figure 8. +5 V Only 18-Bit Stereo DAC