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
example, V
OS
can be a few hundred microvolts or less, combined
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
supply comparator has a V
OS
less than 200 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
100V
25kV
0V
–2.5V
+2.5V
t
r
= t
f
= 5ms
610mV OVERDRIVE
1/2
OP113
10
90
100
0%
2V
2V
5ms
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
®
Stereo Codec device. The pseudo-
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
5kV
OPTIONAL
GAIN
1kV
V
REF
1/2
OP213
+5V
V
REF
OPTIONAL
GAIN
1kV
5kV
29
19
31
10kV
LOUT1L
LOUT1R
CMOUT
AD1849
V
REF
10mF
10kV
L VOLUME
CONTROL
R VOLUME
CONTROL
16V
220mF
47kV
HEADPHONE
LEFT
HEADPHONE
RIGHT
10mF
+
16V
220mF
47kV
+
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
10kV
50V
10mF
20V
100V10kV
+5V
1/2
OP213
20V
50V
10mF
10kV
1/2
OP213
10kV
100V
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.
