REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
AD8614/AD8644
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 1999
Single and Quad +18 V
Operational Amplifiers
PIN CONFIGURATIONS
5-Lead SOT-23
(RT Suffix)
1
2
3
5
4
IN
+IN
V+
OUT A
AD8614
V
14-Lead TSSOP
(RU Suffix)
OUT A
IN A
IN A
V
IN D
IN D
V
OUT D
1
14
IN B
IN B
OUT B
IN C
OUT C
IN C
7
8
AD8644
14-Lead Narrow Body SO
(R Suffix)
14
13
12
11
10
9
8
1
2
3
4
5
6
7
IN A
+IN A
V+
+IN B
IN B
OUT B
OUT D
IN D
+IN D
V
+IN C
IN C
OUT C
OUT A
AD8644
FEATURES
Unity Gain Bandwidth: 5.5 MHz
Low Voltage Offset: 1.0 mV
Slew Rate: 7.5 V/ s
Single-Supply Operation: 5 V to 18 V
High Output Current: 70 mA
Low Supply Current: 800 A/Amplifier
Stable with Large Capacitive Loads
Rail-to-Rail Inputs and Outputs
APPLICATIONS
LCD Gamma and V
COM
Drivers
Modems
Portable Instrumentation
Direct Access Arrangement
GENERAL DESCRIPTION
The AD8614 (single) and AD8644 (quad) are single-supply,
5.5 MHz bandwidth, rail-to-rail amplifiers optimized for LCD
monitor applications.
They are processed using Analog Devices high voltage, high speed,
complementary bipolar process--HV XFCB. This proprietary
process includes trench isolated transistors that lower internal
parasitic capacitance which improves gain bandwidth, phase mar-
gin and capacitive load drive. The low supply current of 800
A
(typ) per amplifier is critical for portable or densely packed designs.
In addition, the rail-to-rail output swing provides greater dynamic
range and control than standard video amplifiers provide.
These products operate from supplies of 5 V to as high as
18 V. The unique combination of an output drive of 70 mA,
high slew rates, and high capacitive drive capability makes the
AD8614/AD8644 an ideal choice for LCD applications.
The AD8614 and AD8644 are specified over the temperature
range of 20
C to +85
C. They are available in 5-lead SOT-23,
14-lead TSSOP and 14-lead SOIC surface mount packages in
tape and reel.
2
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AD8614/AD8644SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
INPUT CHARACTERISTICS
Offset Voltage
V
OS
1.0
2.5
mV
20
C
T
A
+85
C
3
mV
Input Bias Current
I
B
80
400
nA
20
C
T
A
+85
C
500
nA
Input Offset Current
I
OS
5
100
nA
20
C
T
A
+85
C
200
nA
Input Voltage Range
0
V
S
V
Common-Mode Rejection Ratio
CMRR
V
CM
= 0 V to V
S
60
75
dB
Voltage Gain
A
VO
V
OUT
= 0.5 V to V
S
0.5 V, R
L
= 10 k
10
150
V/mV
OUTPUT CHARACTERISTICS
Output Voltage High
V
OH
I
LOAD
= 10 mA
V
S
0.15
V
Output Voltage Low
V
OL
I
LOAD
= 10 mA
65
150
mV
Output Short Circuit Current
I
SC
35
70
mA
20
C
T
A
+85
C
30
mA
POWER SUPPLY
PSRR
PSRR
V
S
=
2.25 V to
9.25 V
80
110
dB
Supply Current / Amplifier
Isy
0.8
1.1
mA
20
C
T
A
+85
C
1.5
mA
DYNAMIC PERFORMANCE
Slew Rate
SR
C
L
= 200 pF
7.5
V/
s
Gain Bandwidth Product
GBP
5.5
MHz
Phase Margin
o
65
Degrees
Settling Time
t
S
0.01%, 10 V Step
3
s
NOISE PERFORMANCE
Voltage Noise Density
e
n
f = 1 kHz
12
nV/
Hz
e
n
f = 10 kHz
11
nV/
Hz
Current Noise Density
i
n
f = 10 kHz
1
pA/
Hz
NOTE
All typical values are for V
S
= 18 V.
Specifications subject to change without notice.
(5 V
V
S
18 V, V
CM
= V
S
/2, T
A
= 25 C unless otherwise noted)
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD8614/AD8644 features proprietary ESD protection circuitry, permanent dam-
age may occur on devices subjected to high energy electrostatic discharges. Therefore, proper
ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND to V
S
Storage Temperature Range . . . . . . . . . . . . 65
C to +150
C
Operating Temperature Range . . . . . . . . . . . 20
C to +85
C
Junction Temperature Range . . . . . . . . . . . . 65
C to +150
C
Lead Temperature Range (Soldering, 60 sec) . . . . . . . . 300
C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating condi-
tions for extended periods may affect device reliability.
Package Type
JA
1
JC
Unit
5-Lead SOT-23 (RT)
230
140
C/W
14-Lead TSSOP (RU)
180
35
C/W
14-Lead SOIC (R)
120
56
C/W
NOTE
1
JA
is specified for worst-case conditions, i.e.,
JA
is specified for device soldered
onto a circuit board for surface mount packages.
ORDERING GUIDE
Temperature
Package
Package
Model
Range
Description
Option
AD8614ART
1
20
C to +85
C
5-Lead SOT-23
RT-5
AD8644ARU
2
20
C to +85
C
14-Lead TSSOP RU-14
AD8644AR
2
20
C to +85
C
14-Lead SOIC
R-14
NOTES
1
Available in 3,000 or 10,000 piece reels.
2
Available in 2,500 piece reels only.
AD8614/AD8644
3
REV. 0
Typical Performance Characteristics
CAPACITANCE pF
10
10k
100
1k
50
45
0
40
35
30
25
20
15
10
5
V
S
= 18V
R
L
= 2k
T
A
= 25 C
+OS
OS
SMALL SIGNAL OVERSHOOT %
Figure 1. Small Signal Overshoot vs.
Load Capacitance
SETTLING TIME s
OUTPUT SWING FROM 0 TO
V
12
12
0
0.5
3.5
1.0
1.5
2.0
2.5
3.0
8
4
0
4
8
0.1%
0.01%
0.1%
0.01%
Figure 2. Settling Time
GAIN dB
FREQUENCY Hz
1k
100M
10k
100k
1M
10M
80
60
40
20
0
45
90
135
180
5V V
S
18V
R
L
= 1M
C
L
= 40pF
T
A
= 25 C
PHASE SHIFT Degrees
Figure 3. Open-Loop Gain and Phase
vs. Frequency
TIME 1 s/Div
V
S
= 5V
R
L
= 2k
C
L
= 200pF
A
V
= 1
T
A
= 25 C
VOLTAGE 1V/Div
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0.5
0.5
1.5
2.5
Figure 4. Large Signal Transient
Response
TIME 1 s/Div
V
S
= 18V
R
L
= 2k
C
L
= 200pF
A
V
= 1
T
A
= 25 C
VOLTAGE 4V/Div
29
25
21
17
13
9
5
1
3
7
11
Figure 5. Large Signal Transient
Response
TIME 500ns/Div
V
S
= 5V V
S
18V
R
L
= 2k
C
L
= 200pF
A
V
= 1
T
A
= 25 C
V
S
2
VOLTAGE 50mV/Div
Figure 6. Small Signal Transient
Response
LOAD CURRENT mA
10
1
0.001
100
0.01
0.1
1
10
100
1k
SOURCE
SINK
5V V
S
18V
T
A
= 25 C
10k
OUTPUT VOLTAGE mV
Figure 7. Output Voltage to Supply
Rail vs. Load Current
SUPPLY VOLTAGE Volts
1,000
400
0
0
10
1
2
3
4
5
6
7
8
9
900
500
300
100
700
600
200
800
T
A
= 25 C
SUPPLY CURRENT/AMPLIFIER
A
Figure 8. Supply Current vs. Supply
Voltage
COMMON-MODE VOLTAGE Volts
400
0
400
2.5
2.5
1.5
0.5
0.5
1.5
300
200
200
300
100
100
V
S
= 2.5V
INPUT BIAS CURRENT nA
Figure 9. Input Bias Current vs.
Common-Mode Voltage
AD8614/AD8644
4
REV. 0
COMMON-MODE VOLTAGE Volts
400
0
400
9
9
7
5
3
1
0
1
3
5
7
300
200
200
300
100
100
V
S
= 9V
INPUT BIAS CURRENT nA
Figure 10. Input Bias Current vs.
Common-Mode Voltage
INPUT OFFSET VOLTAGE mV
2
2
0
0.5
1
1.5
QUANTITY Amplifiers
180
160
0
80
60
40
20
140
100
120
1.5
1
0.5
2.5V V
S
9V
T
A
= 25 C
Figure 11. Input Offset Voltage
Distribution
TEMPERATURE C
SUPPLY CURRENT/AMPLIFIER mA
1.0
0.9
0.5
35
15
5
25
45
65
85
0.8
0.7
0.6
V
S
= 18V
V
S
= 5V
Figure 12. Supply Current vs.
Temperature
FREQUENCY Hz
OUTPUT SWING V p-p
6
5
0
100
1k
10M
10k
100k
1M
4
3
2
1
V
S
= 5V
A
VCL
= 1
R
L
= 2k
T
A
= 25 C
Figure 13. Maximum Output Swing
vs. Frequency
FREQUENCY Hz
OUTPUT SWING V p-p
20
18
0
100
1k
10M
10k
100k
1M
10
6
2
V
S
= 18V
A
VCL
= 1
R
L
= 2k
T
A
= 25 C
4
8
16
14
12
Figure 14. Maximum Output Swing
vs. Frequency
FREQUENCY Hz
IMPEDANCE
300
240
0
1k
10k
100k
1M
10M
180
120
60
5V V
S
18V
T
A
= 25 C
A
V
= 100
A
V
= 10
A
V
= 1
Figure 15. Closed-Loop Output
Impedance vs. Frequency
FREQUENCY Hz
GAIN dB
40
1k
10k
100M
100k
1M
10M
20
0
5V V
S
18V
T
A
= 25 C
Figure 16. Closed-Loop Gain vs.
Frequency
FREQUENCY Hz
COMMON-MODE REJECTION dB
100
100
1k
10M
10k
100k
1M
80
60
5V V
S
18V
T
A
= 25 C
0
20
40
120
140
Figure 17. Common-Mode Rejection
vs. Frequency
FREQUENCY Hz
POWER-SUPPLY REJECTION dB
100
1k
10k
100k
1M
100
0
80
60
40
20
10M
V
S
= 18V
T
A
= 25 C
PSRR+
PSRR
Figure 18. Power-Supply Rejection
vs. Frequency
AD8614/AD8644
5
REV. 0
SUPPLY VOLTAGE V
0
2
20
4
6
8
10
12
14 16
18
SLEW RATE V/
s
9
8
0
4
3
2
1
7
5
6
A
V
= 1
R
L
= 2k
C
L
= 200pF
T
A
= 25 C
SR+
SR
Figure 19. Slew Rate vs. Supply
Voltage
VOLTAGE NOISE DENSITY nV Hz
FREQUENCY Hz
100
10
1
10
100
10k
1k
V
S
= 5V
T
A
= 25 C
Figure 20. Voltage Noise Density
vs. Frequency
VOLTAGE NOISE DENSITY nV Hz
FREQUENCY Hz
100
10
1
10
100
10k
1k
V
S
= 18V
T
A
= 25 C
Figure 21. Voltage Noise Density vs.
Frequency
APPLICATIONS SECTION
Theory of Operation
The AD8614/AD8644 are processed using Analog Devices' high
voltage, high speed, complementary bipolar process--HV XFCB.
This process includes trench isolated transistors that lower parasitic
capacitance.
Figure 22 shows a simplified schematic of the AD8614/AD8644.
The input stage is rail-to-rail, consisting of two complementary
differential pairs, one NPN pair and one PNP pair. The input stage
is protected against avalanche breakdown by two back-to-back
diodes. Each input has a 1.5 k
resistor that limits input current
during over-voltage events and furnishes phase reversal protection
if the inputs are exceeded. The two differential pairs are connected
to a double-folded cascode. This is the stage in the amplifier with
the most gain. The double folded cascode differentially feeds the
output stage circuitry. Two complementary common emitter tran-
sistors are used as the output stage. This allows the output to swing
to within 125 mV from each rail with a 10 mA load. The gain of the
output stage, and thus the open loop gain of the op amp, depends on
the load resistance.
V
CC
+
1.5k
V
EE
V
CC
V
OUT
1.5k
V
CC
Figure 22. Simplified Schematic
The AD8614/AD8644 have no built-in short circuit protection.
The short circuit limit is a function of high current roll-off of the
output stage transistors and the voltage drop over the resistor
shown on the schematic at the output stage. The voltage over this
resistor is clamped to one diode during short circuit voltage events.
Output Short-Circuit Protection
To achieve a wide bandwidth and high slew rate, the output of
the AD8614/AD8644 is not short-circuit protected. Shorting
the output directly to ground or to a supply rail may destroy the
device. The typical maximum safe output current is 70 mA.
In applications where some output current protection is needed,
but not at the expense of reduced output voltage headroom, a low
value resistor in series with the output can be used. This is shown
in Figure 23. The resistor is connected within the feedback loop
of the amplifier so that if V
OUT
is shorted to ground and V
IN
swings up to 18 V, the output current will not exceed 70 mA.
For 18 V single supply applications, resistors less than 261
are
not recommended.
AD8614/AD8644
6
REV. 0
AD86x4
V
IN
261
V
OUT
18V
Figure 23. Output Short-Circuit Protection
Input Overvoltage Protection
As with any semiconductor device, whenever the condition exists for
the input to exceed either supply voltage, attention needs to be paid
to the input overvoltage characteristic. As an overvoltage occurs, the
amplifier could be damaged, depending on the voltage level and the
magnitude of the fault current. When the input voltage exceeds
either supply by more than 0.6 V, internal pin junctions energize,
allowing current to flow from the input to the supplies. Observing
Figure 22, the AD8614/AD8644 has 1.5 k
resistors in series with
each input, which helps limit the current. This input current is not
inherently damaging to the device as long as it is limited to 5 mA or
less. If the voltage is large enough to cause more than 5 mA of cur-
rent to flow, an external series resistor should be added. The size of
this resistor is calculated by dividing the maximum overvoltage by
5 mA and subtracting the internal 1.5 k
resistor. For example, if
the input voltage could reach 100 V, the external resistor should be
(100 V/5 mA) 1.5 k
= 18.5 k
. This resistance should be placed
in series with either or both inputs if they are subjected to the over-
voltages. For more information on general overvoltage characteristics
of amplifiers refer to the 1993 System Applications Guide, available
from the Analog Devices Literature Center.
Output Phase Reversal
The AD8614/AD8644 is immune to phase reversal as long as the
input voltage is limited to within the supply rails. Although the
device's output will not change phase, large currents due to
input overvoltage could result, damaging the device. In applica-
tions where the possibility of an input voltage exceeding the
supply voltage exists, overvoltage protection should be used, as
described in the previous section.
Power Dissipation
The maximum power that can be safely dissipated by the
AD8614/AD8644 is limited by the associated rise in junction
temperature. The maximum safe junction temperature is 150
C,
and should not be exceeded or device performance could suffer.
If this maximum is momentarily exceeded, proper circuit opera-
tion will be restored as soon as the die temperature is reduced.
Leaving the device in an "overheated" condition for an extended
period can result in permanent damage to the device.
To calculate the internal junction temperature of the AD86x4,
the following formula can be used:
T
J
= P
DISS
JA
+ T
A
where: T
J
= AD86x4 junction temperature;
P
DISS
= AD86x4 power dissipation;
JA
= AD86x4 package thermal resistance, junction-to-
ambient; and
T
A
= Ambient temperature of the circuit.
The power dissipated by the device can be calculated as:
P
DISS
= I
LOAD
(V
S
V
OUT
)
where: I
LOAD
is the AD86x4 output load current;
V
S
is the AD86x4 supply voltage; and
V
OUT
is the AD86x4 output voltage.
Figure 24 provides a convenient way to see if the device is being
overheated. The maximum safe power dissipation can be found
graphically, based on the package type and the ambient tem-
perature around the package. By using the previous equation, it
is a simple matter to see if P
DISS
exceeds the device's power
derating curve. To ensure proper operation, it is important to
observe the recommended derating curves shown in Figure 24.
AMBIENT TEMPERATURE C
1.5
0
35
15
5
25
45
65
85
1.0
0.5
14-LEAD SOIC PACKAGE
JA
= 120 C/W
14-LEAD TSSOP PACKAGE
JA
= 180 C/W
5-LEAD SOT-23 PACKAGE
JA
= 230 C/W
MAXIMUM POWER DISSIPATION Watts
Figure 24. Maximum Power Dissipation vs. Temperature
for 5-Lead and 14-Lead Package Types
Unused Amplifiers
It is recommended that any unused amplifiers in the quad pack-
age be configured as a unity gain follower with a 1 k
feedback
resistor connected from the inverting input to the output, and
the noninverting input tied to the ground plane.
Capacitive Load Drive
The AD8614/AD8644 exhibits excellent capacitive load driving
capabilities. Although the device is stable with large capacitive
loads, there is a decrease in amplifier bandwidth as the capacitive
load increases.
When driving heavy capacitive loads directly from the AD8614/
AD8644 output, a snubber network can be used to improve the
transient response. This network consists of a series R-C connected
from the amplifier's output to ground, placing it in parallel with the
capacitive load. The configuration is shown in Figure 25. Although
this network will not increase the bandwidth of the amplifier, it will
significantly reduce the amount of overshoot.
AD86x4
V
IN
V
OUT
5V
R
X
C
X
C
L
Figure 25. Snubber Network Compensation for Capacitive
Loads
AD8614/AD8644
7
REV. 0
The optimum values for the snubber network should be determined
empirically based on the size of the capacitive load. Table I shows a
few sample snubber network values for a given load capacitance.
Table I. Snubber Networks for Large Capacitive Loads
Load Capacitance
Snubber Network
(C
L
)
(R
S
, C
S
)
0.47 nF
300
, 0.1
F
4.7 nF
30
, 1
F
47 nF
5
, 1
F
Direct Access Arrangement
Figure 26 shows a schematic for a 5 V single supply transmit/receive
telephone line interface for 600
transmission systems. It allows
full duplex transmission of signals on a transformer-coupled 600
line. Amplifier A1 provides gain that can be adjusted to meet the
modem output drive requirements. Both A1 and A2 are configured
to apply the largest possible differential signal to the transformer.
The largest signal available on a single 5 V supply is approximately
4.0 V p-p into a 600
transmission system. Amplifier A3 is config-
ured as a difference amplifier to extract the receive information from
the transmission line for amplification by A4. A3 also prevents the
transmit signal from interfering with the receive signal. The gain of
A4 can be adjusted in the same manner as A1's to meet the modem's
input signal requirements. Standard resistor values permit the use of
SIP (Single In-Line Package) format resistor arrays. Couple this with
the AD8644 14-lead SOIC or TSSOP package and this circuit can
offer a compact solution.
6.2V
6.2V
TRANSMIT
TxA
RECEIVE
RxA
C1
0.1 F
R1
10k
R2
9.09k
2k
P1
Tx GAIN
ADJUST
A1
A2
A3
A4
A1, A2 = 1/2 AD8644
A3, A4 = 1/2 AD8644
R3
360
1:1
T1
TO TELEPHONE
LINE
1
2
3
7
6
5
2
3
1
6
5
7
10 F
R7
10k
R8
10k
R5
10k
R6
10k
R9
10k
R14
14.3k
R10
10k
R11
10k
R12
10k
R13
10k
C2
0.1 F
P2
Rx GAIN
ADJUST
2k
Z
O
600
5V DC
MIDCOM
671-8005
Figure 26. A Single-Supply Direct Access Arrangement for
Modems
A One-Chip Headphone/Microphone Preamplifier Solution
Because of its high output current performance, the AD8644
makes an excellent amplifier for driving an audio output jack in
a computer application. Figure 27 shows how the AD8644 can
be interfaced with an ac codec to drive headphones or speakers
U1-A
R1
2k
4
C1
100 F
5V
1
10
2
3
5
5V
V
DD
V
DD
LEFT
OUT
AD1881
(AC'97)
RIGHT
OUT
V
SS
R3
20
7
8
6
9
R4
20
C2
100 F
NOTE: ADDITIONAL PINS
OMITTED FOR CLARITY
U1-B
U1 = AD8644
R2
2k
28
35
36
Figure 27. A PC-99 Compliant Headphone/Line Out Amplifier
If gain is required from the output amplifier, four additional
resistors should be added as shown in Figure 28. The gain of
the AD8644 can be set as:
A
R
R
V
=
6
5
U1-A
R1
2k
4
C1
100 F
5V
1
10
2
3
5
5V
V
DD
V
DD
LEFT
OUT
AD1881
(AC97)
RIGHT
OUT
V
SS
R3
20
7
8
6
9
R4
20
C2
100 F
NOTE: ADDITIONAL PINS
OMITTED FOR CLARITY
U1-B
U1 = AD8644
R2
2k
R6
20k
R6
20k
V
REF
R5
10k
R5
10k
A
V
=
= +6dB WITH VALUES SHOWN
R6
R5
38
35
27
36
Figure 28. A PC-99-Compliant Headphone/Speaker
Amplifier with Gain
Input coupling capacitors are not required for either circuit as
the reference voltage is supplied from the AD1881.
R4 and R5 help protect the AD8644 output in case the output
jack or headphone wires are accidentally shorted to ground.
The output coupling capacitors C1 and C2 block dc current
from the headphones and create a high-pass filter with a corner
frequency of:
f
C R
R
dB
L
-
=
+
(
)
3
1
2
1
4
Where R
L
is the resistance of the headphones.
8
REV. 0
C3735810/99
PRINTED IN U.S.A.
AD8614/AD8644
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
5-Lead SOT-23
(RT Suffix)
0.1181 (3.00)
0.1102 (2.80)
PIN 1
0.0669 (1.70)
0.0590 (1.50)
0.1181 (3.00)
0.1024 (2.60)
1
3
4
5
0.0748 (1.90)
BSC
0.0374 (0.95) BSC
2
0.0079 (0.20)
0.0031 (0.08)
0.0217 (0.55)
0.0138 (0.35)
10
0
0.0197 (0.50)
0.0138 (0.35)
0.0059 (0.15)
0.0019 (0.05)
0.0512 (1.30)
0.0354 (0.90)
SEATING
PLANE
0.0571 (1.45)
0.0374 (0.95)
14-Lead TSSOP
(RU Suffix)
14
8
7
1
0.201 (5.10)
0.193 (4.90)
0.256 (6.50)
0.246 (6.25)
0.177 (4.50)
0.169 (4.30)
PIN 1
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.0118 (0.30)
0.0075 (0.19)
0.0256
(0.65)
BSC
0.0433
(1.10)
MAX
0.0079 (0.20)
0.0035 (0.090)
0.028 (0.70)
0.020 (0.50)
8
0
14-Lead Narrow SOIC
(R Suffix)
14
8
7
1
0.3444 (8.75)
0.3367 (8.55)
0.2440 (6.20)
0.2284 (5.80)
0.1574 (4.00)
0.1497 (3.80)
PIN 1
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.0192 (0.49)
0.0138 (0.35)
0.0688 (1.75)
0.0532 (1.35)
0.0500
(1.27)
BSC
0.0099 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
0
0.0196 (0.50)
0.0099 (0.25)
x 45
The remaining two amplifiers can be used as low voltage
microphone preamplifiers. A single AD8614 can be used as a
stand-alone microphone preamplifier. Figure 29 shows this
implementation.
AD1881
(AC'97)
V
REF
10k
21
MIC 1 IN
A
V
= 20dB
1k
1 F
2.2k
5V
10k
A
V
= +20dB
1k
1 F
2.2k
5V
MIC 1
MIC 2
22
MIC 2 IN
27
Figure 29. Microphone Preamplifier
SPICE Model Availability
The SPICE model for the AD8614/AD8644 amplifier is available
and can be downloaded from the Analog Devices' web site at
http://www.analog.com. The macro-model accurately simulates
a number of AD8614/AD8644 parameters, including offset volt-
age, input common-mode range, and rail-to-rail output swing.
The output voltage versus output current characteristic of the
macro-model is identical to the actual AD8614/AD8644 perfor-
mance, which is a critical feature with a rail-to-rail amplifier model.
The model also accurately simulates many ac effects, such as gain
bandwidth product, phase margin, input voltage noise, CMRR and
PSRR versus frequency, and transient response. Its high degree of
model accuracy makes the AD8614/AD8644 macro-model one of
the most reliable and true-to-life models available for any amplifier.
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