OP113/OP213/OP413

–8–

REV. C

Precision Voltage Comparator

With its PNP inputs and zero volt common-mode capability, the

OP113 family can make useful voltage comparators. There is

only a slight penalty in speed in comparison to IC comparators.

However, the significant advantage is its voltage accuracy. For

with CMRR and PSRR exceeding 100 dB, while operating on

5 V supply. Standard comparators like the 111/311 family oper-

ate on 5 volts, but not with common-mode at ground, nor with

offset below 3 mV. Indeed, no commercially available single

µV.

Figure 11 shows the OP113 family response to a 10 mV over-

drive signal when operating in open loop. The top trace shows

the output rising edge has a 15

µs propagation delay, while the

bottom trace shows a 7

µs delay on the output falling edge. This

ac response is quite acceptable in many applications.

+5V

100

25k

0V

–2.5V

+2.5V

10mV OVERDRIVE

1/2

OP113

10

90

100

0%

2V

2V

5 s

Figure 11. Precision Comparator

The low noise and 250

µV (maximum) offset voltage enhance

the overall dc accuracy of this type of comparator. Note that

zero crossing detectors and similar ground referred comparisons

can be implemented even if the input swings to –0.3 volts below

ground.

Low Voltage Headphone Amplifiers

Figure 9 shows a stereo headphone output amplifier for the

AD1849 16-bit SoundPort

reference voltage is derived from the common-mode voltage

generated internally by the AD1849, thus providing a conve-

nient bias for the headphone output amplifiers.

1/2

OP213

+5V

1/2

OP213

5k

OPTIONAL

GAIN

1k

1/2

OP213

+5V

OPTIONAL

GAIN

1k

5k

29

19

31

10k

LOUT1L

LOUT1R

CMOUT

AD1849

10 F

10k

L VOLUME

CONTROL

R VOLUME

CONTROL

16

220 F

47k

HEADPHONE

LEFT

HEADPHONE

RIGHT

10 F

+

16

220 F

47k

+

Figure 9. Headphone Output Amplifier for Multimedia

Sound Codec

Low Noise Microphone Amplifier for Multimedia

The OP113 family is ideally suited as a low noise microphone

preamp for low voltage audio applications. Figure 10 shows a

gain of 100 stereo preamp for the AD1849 16-bit SoundPort

Stereo Codec chip. The common-mode output buffer serves as

a “phantom power” driver for the microphones.

+5V

1/2

OP213

10k

50

10 F

20

100

10k

+5V

1/2

OP213

20

50

10 F

10k

1/2

OP213

10k

100

15

17

MINL

MINR

CMOUT

AD1849

RIGHT

ELECTRET

CONDENSER

MIC

INPUT

LEFT

ELECTRET

CONDENSER

MIC

INPUT

19

Figure 10. Low Noise Stereo Microphone Amplifier for

Multimedia Sound Codec

SoundPort is a registered trademark of Analog Device, Inc.