ETC OPA342/OPA2342/OPA4342

®
OPA
342
OPA
234
2
OPA
OPA
434
®
342
2
OPA342
OPA2342
OPA4342
For most current data sheet and other product
information, visit www.burr-brown.com
Low Cost, Low Power, Rail-to-Rail
OPERATIONAL AMPLIFIERS
MicroAmplifier ™ Series
FEATURES
DESCRIPTION
LOW QUIESCENT CURRENT: 150µA typ
RAIL-TO-RAIL INPUT
RAIL-TO-RAIL OUTPUT (within 1mV)
SINGLE SUPPLY CAPABILITY
LOW COST
MicroSIZE PACKAGE OPTIONS:
SOT-23-5
MSOP-8
TSSOP-14(1)
● BANDWIDTH: 1MHz
● SLEW RATE: 1V/µs
● THD + NOISE: 0.006%
The OPA342 series rail-to-rail CMOS operational
amplifiers are designed for low cost, low power,
miniature applications. They are optimized to operate
on a single supply as low as 2.5V with an input
common-mode voltage range that extends 300mV
beyond the supplies.
●
●
●
●
●
●
APPLICATIONS
● COMMUNICATIONS
● PCMCIA CARDS
● DATA ACQUISITION
● PROCESS CONTROL
● AUDIO PROCESSING
● ACTIVE FILTERS
● TEST EQUIPMENT
● CONSUMER ELECTRONICS
Rail-to-rail input/output and high-speed operation make
them ideal for driving sampling analog-to-digital converters. They are also well suited for general purpose
and audio applications and providing I/V conversion
at the output of digital-to-analog converters. Single,
dual, and quad versions have identical specs for design
flexibility.
The OPA342 series offers excellent dynamic response
with a quiescent current of only 250µA max. Dual and
quad designs feature completely independent circuitry
for lowest crosstalk and freedom from interaction.
The OPA342 is available in the microsize SOT-23-5
and SO-8 packages. The OPA2342 is available in the
MSOP-8 and SO-8 packages. The OPA4342 is available in TSSOP-14(1) and SO-14 packages. All are
specified for operation from –40°C to +85°C. A SPICE
macromodel is available for design analysis.
NOTE: (1) TSSOP-14 package available Q4’99.
SPICE MODEL available at www.burr-brown.com.
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111
Twx: 910-952-1111 • Internet: http://www.burr-brown.com/ • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
®
© 1999 Burr-Brown Corporation
PDS-1485A
1
Printed in U.S.A. July, 1999
OPA342, OPA2342, OPA4342
SPECIFICATIONS: VS = 2.7V to 5.5V
At TA = +25°C, RL = 10kΩ connected to VS /2 and VOUT = VS /2, unless otherwise noted.
Boldface limits apply over the specified temperature range, TA = –40°C to +85°C.
OPA342NA, UA
OPA2342EA, UA
OPA4342EA(1), UA
PARAMETER
CONDITION
OFFSET VOLTAGE
Input Offset Voltage
TA = –40°C to +85°C
vs Temperature
vs Power Supply
TA = –40°C to +85°C
Channel Separation, dc
f = 1kHz
VOS
dVOS /dT
PSRR
±1
VCM = VS /2
VS = 2.7V to 5.5V, VCM < (V+) – 1.8V
VS = 2.7V to 5.5V, VCM < (V+) – 1.8V
mV
mV
µV/°C
µV/V
µV/V
µV/V
dB
200
200
8
30
3
VCM
CMRR
CMRR
CMRR
AOL
FREQUENCY RESPONSE
Gain-Bandwidth Product
GBW
Slew Rate
SR
Settling Time, 0.1%
0.01%
Overload Recovery Time
Total Harmonic Distortion + Noise, f = 1kHz THD+N
OUTPUT
Voltage Output Swing from Rail(3)
TA = –40°C to +85°C
TEMPERATURE RANGE
Specified Range
Operating Range
Storage Range
Thermal Resistance
SOT-23-5 Surface Mount
MSOP-8 Surface Mount
SO-8 Surface Mount
TSSOP-14 Surface Mount(1)
SO-14 Surface Mount
±6
30
en
in
TA = –40°C to +85°C
POWER SUPPLY
Specified Voltage Range
Operating Voltage Range
Quiescent Current (per amplifier)
TA = –40°C to +85°C
UNITS
±6
IOS
VS = +5.5V, –0.3V < VCM < (V+) – 1.8V
VS = +5.5V, –0.3V < VCM < (V+) – 1.8V
VS = +5.5V, –0.3V < VCM < 5.8V
VS = +5.5V, –0.3V < VCM < 5.8V
VS = +2.7V, –0.3V < VCM < 3V
VS = +2.7V, –0.3V < VCM < 3V
–0.3
76
74
66
64
62
60
INPUT IMPEDANCE
Differential
Common-Mode
TA = –40°C to +85°C
Short-Circuit Current
Capacitive Load Drive
MAX
±1
±3
±0.2
See Typical Curve
±0.2
IB
NOISE
Input Voltage Noise, f = 0.1Hz to 50kHz
Input Voltage Noise Density, f = 1kHz
Current Noise Density, f = 1kHz
OPEN-LOOP GAIN
Open-Loop Voltage Gain
TA = –40°C to +85°C
TYP
0.2
132
INPUT BIAS CURRENT
Input Bias Current
TA = –40°C to +85°C
Input Offset Current
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
TA = –40°C to +85°C
Common-Mode Rejection Ratio
TA = –40°C to +85°C
Common-Mode Rejection Ratio
TA = –40°C to +85°C
MIN
ISC
CLOAD
RL = 100kΩ, 10mV < VO < (V+) – 10mV
RL = 100kΩ, 10mV < VO < (V+) – 10mV
RL = 5kΩ, 400mV < VO < (V+) – 400mV
RL = 5kΩ, 400mV < VO < (V+) – 400mV
106
100
96
90
CL = 100pF
G=1
G=1
VS = 5.5V, 2V Step
VS = 5.5V, 2V Step
VIN • G = VS
VS = 5.5V, VO = 3Vp-p(2), G = 1
IQ
±10
(V+) + 0.3
88
78
74
V
dB
dB
dB
dB
dB
dB
1013 || 3
1013 || 6
Ω || pF
Ω || pF
124
dB
dB
dB
dB
114
1
3
20
MHz
V/µs
µs
µs
µs
%
10
10
400
400
±15
See Typical Curve
2.7
5.5
2.5 to 5.5
150
IO = 0A
pA
pA
pA
µVrms
nV/√Hz
fA/√Hz
1
1
5
8
2.5
0.006
RL = 100kΩ, AOL ≥ 96dB
RL = 100kΩ, AOL ≥ 106dB
RL = 100kΩ, AOL ≥ 100dB
RL = 5kΩ, AOL ≥ 96dB
RL = 5kΩ, AOL ≥ 90dB
Per Channel
VS
±10
–40
–55
–65
θJA
200
150
150
100
100
mV
mV
mV
mV
mV
mA
250
300
V
V
µA
µA
+85
+125
+150
°C
°C
°C
°C/W
°C/W
°C/W
°C/W
°C/W
NOTES: (1) OPA4342EA available 4Q’99. (2) VOUT = 0.25V to 3.25V. (3) Output voltage swings are measured between the output and power supply rails.
®
OPA342, OPA2342, OPA4342
2
ABSOLUTE MAXIMUM RATINGS(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
Supply Voltage, V+ to V– ................................................................... 5.5V
Signal Input Terminals, Voltage(2) .................. (V–) – 0.5V to (V+) + 0.5V
Current(2) .................................................... 10mA
Output Short Circuit(3) .............................................................. Continuous
Operating Temperature .................................................. –55°C to +125°C
Storage Temperature ..................................................... –65°C to +150°C
Junction Temperature ...................................................................... 150°C
Lead Temperature (soldering, 3s) ................................................... 240°C
ESD Capability (Human Body Model) ............................................. 4000V
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet its
published specifications.
NOTES: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade device reliability. (2) Input terminals are diode-clamped to the power
supply rails. Input signals that can swing more than 0.5V beyond the supply
rails should be current-limited to 10mA or less. (3) Short circuit to ground,
one amplifier per package.
PACKAGE/ORDERING INFORMATION
PRODUCT
PACKAGE
PACKAGE
DRAWING
NUMBER(1)
OPA342NA
SOT-23-5
331
–40°C to +85°C
B42
"
"
"
"
OPA342UA
"
OPA342UA
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER(2)
TRANSPORT
MEDIA
OPA342NA /250
OPA342NA/3K
OPA342UA
OPA342UA/2K5
Tape and Reel
Tape and Reel
Rails
Tape and Reel
Tape and Reel
Tape and Reel
Rails
Tape and Reel
SO-8
182
–40°C to +85°C
"
"
"
"
"
OPA2342EA
"
OPA2342UA
MSOP-8
"
SO-8
337
"
182
–40°C to +85°C
"
–40°C to +85°C
C42
"
OPA2342UA
"
"
"
"
"
OPA2342EA/250
OPA2342EA/2K5
OPA2342UA
OPA2342UA/2K5
OPA4342EA✻
"
TSSOP-14
"
357
"
–40°C to +85°C
"
OPA4342EA
"
OPA4342EA/250
OPA4342EA/2K5
Tape and Reel
Tape and Reel
OPA4342UA
SO-14
235
–40°C to +85°C
OPA4342UA
"
"
"
"
"
OPA4342UA
OPA4342UA/2K5
Rails
Tape and Reel
NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) are
available only in Tape and Reel in the quantities indicated (e.g., /3K indicates 3000 devices per reel). Ordering 3000 pieces of “OPA342NA/3K” will get a single
3000-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book.
✻ OPA4342EA available 4Q’99.
PIN CONFIGURATIONS
OPA4342
OPA342
V+
Out A
1
2
–In A
2
3
–In
+In A
3
+V
4
+In B
5
Out
1
V–
+In
5
A
4
14
Out D
13
–In D
12
+In D
11
–V
10
+In C
D
SOT-23-5
B
OPA2342
OPA342
NC
1
8
NC
Out A
1
–In A
2
–In
2
7
V+
+In
3
6
Out
+In A
3
V–
4
5
NC
V–
4
SO-8
A
B
8
V+
7
Out B
6
–In B
5
+In B
C
–In B
6
9
–In C
Out B
7
8
Out C
TSSOP-14(1), SO-14
SO-8, MSOP-8
NOTE: (1) TSSOP-14 available 4Q’99.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility
for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or
licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support
devices and/or systems.
®
3
OPA342, OPA2342, OPA4342
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VS = +5V, and RL = 10kΩ, unless otherwise noted.
POWER SUPPLY AND COMMON-MODE
REJECTION RATIO vs FREQUENCY
OPEN-LOOP GAIN/PHASE vs FREQUENCY
0°
100
100
30°
80
80
60°
60
90°
40
120°
120
+PSRR
Rejection Ratio (dB)
Phase
Phase Shift (°)
Voltage Gain (dB)
Gain
CMRR
–PSRR
60
40
20
20
150°
0
0.1
1
10
100
1k
10k
100k
1M
10
180°
10M
10
100
Frequency (Hz)
100k
140
VS = 5V
5
Channel Separation (dB)
Maximum Output Voltage (V)
10k
CHANNEL SEPARATION vs FREQUENCY
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
6
4
3
VS = 2.7V
2
1
120
100
Dual and quad devices.
G = 1, all channels.
Quad measured channel
A to D or B to C—other
combinations yield improved
rejection.
80
60
0
100
1k
10k
100k
1M
10k
100k
Frequency (Hz)
VOLTAGE AND CURRENT NOISE
SPECTRAL DENSITY vs FREQUENCY
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
1000
100
iN
eN
10
100
10
100
1k
10k
100k
1M
0.1
0.010
0.001
1
10M
20
Frequency (Hz)
100
1k
Frequency (Hz)
®
OPA342, OPA2342, OPA4342
1M
1
THD+N (%)
1000
10
1k
Frequency (Hz)
10000
1
100
10M
Curve Noise fA/√Hz
10
Voltage Noise nV/√Hz
1k
Frequency (Hz)
4
10k
20k
TYPICAL PERFORMANCE CURVES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ, unless otherwise noted.
OPEN-LOOP GAIN, COMMON-MODE REJECTION RATIO,
AND POWER SUPPLY REJECTION vs TEMPERATURE
INPUT BIAS CURRENT vs TEMPERATURE
1000
140
AOL
Input Bias Current (pA)
100
CMRR
80
PSRR
60
40
100
10
Measurement Limited
20
0
1
–75
–50
–25
0
25
50
75
100
125
150
–75
–50
–25
0
QUIESCENT CURRENT AND
SHORT-CIRCUIT CURRENT vs TEMPERATURE
135
25
+ISC
20
–ISC
15
50
10
25
5
Slew Rate (V/µs)
30
75
125
0.8
+SR
0.6
0.4
0.2
0
0
0
25
–75 –50
150
–25
0
25
50
75
100 125 150 175
Temperature (°C)
Temperature (°C)
INPUT BIAS CURRENT
vs COMMON-MODE VOLTAGE
QUIESCENT CURRENT AND
SHORT-CIRCUIT CURRENT vs SUPPLY VOLTAGE
160
6
20
+ISC
Quiescent Current (µA)
4
IB and IOS (pA)
125
1
Short-Circuit Current (mA)
Quiescent Current (µA)
150
–25
100
–SR
35
IQ
–75
75
SLEW RATE vs TEMPERATURE
175
75
50
1.2
40
200
100
25
Temperature (°C)
Temperature (°C)
2
0
–2
155
15
–ISC
150
10
IQ
145
5
–4
140
–6
–6
–4
–2
0
2
4
0
0
6
Short-Circuit Current (mA)
AOL, CMRR, PSRR (dB)
120
1
2
3
4
5
6
Supply Voltage (V)
Common-Mode Voltage (V)
®
5
OPA342, OPA2342, OPA4342
TYPICAL PERFORMANCE CURVES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ, unless otherwise noted.
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
3
120
VS = +2.7V
2
1
Open-Loop Gain (dB)
Output Voltage (V)
85°C
25°C
–40°C
0
–1
25°C
–40°C
85°C
110
RL = 100kΩ
100
RL = 5kΩ
90
–2
–3
80
5
0
10
15
20
120
80
60
40
20
Output Voltage Swing from Rail (mV)
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
0
18
24
Typical production
distribution of
packaged units.
Typical production
distribution of
packaged units.
16
Percent of Amplifiers (%)
20
Percent of Amplifiers (%)
100
Output Current (mA)
16
12
8
4
14
12
10
8
6
4
2
0
–6
–5.4
–4.8
–4.2
–3.6
–3
–2.4
–1.8
–1.2
–0.6
0
0.6
1.2
1.8
2.4
3
3.6
4.2
4.8
5.4
6
–10
–9
–8
–7
–6
–5
–4
–3
–2
–1
0
1
2
3
4
5
6
7
8
9
10
0
Offset Voltage (mV)
Offset Voltage Drift (µV/°C)
QUIESCENT CURRENT
PRODUCTION DISTRIBUTION
SETTLING TIME vs CLOSED-LOOP GAIN
400
350
20
Settling Time (µs)
300
16
12
8
250
0.01%
200
150
100
4
0.1%
50
0
<250
<225
<200
<175
<150
<125
<100
<75
<50
<25
0
<0
Percent of Amplifiers (%)
24
1
Quiescent Current (µA)
®
OPA342, OPA2342, OPA4342
10
100
Closed-Loop Gain (V/V)
6
1000
TYPICAL PERFORMANCE CURVES (Cont.)
At TA = +25°C, VS = +5V, and RL = 10kΩ, unless otherwise noted.
LARGE-SIGNAL STEP RESPONSE
VS = ±2.5V, G = +1, RL = 10kΩ, CL = 100pF
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
50
45
40
30
1V/div
G = +5
25
G = –1
20
G = +1
15
10
G = –5
5
0
1
10
100
1k
10k
5µs/div
Load Capacitance (pF)
SMALL-SIGNAL STEP RESPONSE
VS = ±2.5V, G = +1, RL = 10kΩ, CL = 100pF
20mV/div
Overshoot (%)
35
5µs/div
®
7
OPA342, OPA2342, OPA4342
APPLICATIONS INFORMATION
OPERATING VOLTAGE
OPA342 series op amps are fully specified and guaranteed
from +2.7V to +5.5V. In addition, many specifications apply
from –40°C to +85°C. Parameters that vary significantly
with operating voltages or temperature are shown in the
Typical Performance Curves.
OPA342 series op amps are unity-gain stable and can operate on a single supply, making them highly versatile and
easy to use.
Rail-to-rail input and output swing significantly increases
dynamic range, especially in low supply applications.
Figure 1 shows the input and output waveforms for the
OPA342 in unity-gain configuration. Operation is from
±2.5V supplies with a 10kΩ load connected to ground. The
input is a 5Vp-p sinusoid. Output voltage is approximately
4.997Vp-p.
RAIL-TO-RAIL INPUT
The input common-mode voltage range of the OPA342
series extends 300mV beyond the supply rails. This is
achieved with a complementary input stage—an N-channel
input differential pair in parallel with a P-channel differential pair (see Figure 2). The N-channel input pair is active for
input voltages close to the positive rail, typically (V+) –
1.3V to 300mV above the positive supply, while the Pchannel input pair is active for inputs from 300mV below the
negative supply to approximately (V+) – 1.3V. There is a
small transition region, typically (V+) – 1.5V to (V+) –
1.1V, in which both pairs are on. This 400mV transition
region can vary ±300mV with process variation. Thus, the
transition region (both stages on) can range from (V+) –
1.8V to (V+) – 1.4V on the low end, up to (V+) – 1.2V to
(V+) – 0.8V on the high end. Within the 400mV transition
region PSRR, CMRR, offset voltage, offset drift, and THD
may be degraded compared to operation outside this region.
For more information on designing with rail-to-rail input op
amps, see Figure 3 “Design Optimization with Rail-to-Rail
Input Op Amps.”
Power supply pins should be bypassed with 0.01µF ceramic
capacitors.
G = +1, VS = ±2.5V
1V/div
Input
Output (inverted on scope)
5µs/div
FIGURE 1. Rail-to-Rail Input and Output, Gain = +1.
V+
Reference
Current
VIN+
VIN–
VBIAS1
VBIAS2
V–
(Ground)
®
OPA342, OPA2342, OPA4342
8
Class AB
Control
Circuitry
VO
COMMON-MODE REJECTION
The CMRR for the OPA342 is specified in several ways so
the best match for a given application may be used. First, the
CMRR of the device in the common-mode range below the
transition region (VCM < (V+) – 1.8V) is given. This specification is the best indicator of the capability of the device
when the application requires use of one of the differential
input pairs. Second, the CMRR at 5.5V over the entire
common-mode range is specified. Third, the CMRR at 2.7V
over the entire common-mode range is provided. These last
two values include the variations seen through the transition
region.
V+
IOVERLOAD
10mA max
VOUT
OPAx342
VIN
5kΩ
FIGURE 4. Input Current Protection for Voltages Exceeding
the Supply Voltage.
enhances the amplifier’s ability to drive greater capacitive
loads. See the typical performance curve “Small-Signal
Overshoot vs Capacitive Load.”
In unity-gain configurations, capacitive load drive can be
improved by inserting a small (10Ω to 20Ω) resistor RS in
series with the output, as shown in Figure 5. This significantly reduces ringing while maintaining dc performance for
purely capacitive loads. However, if there is a resistive load
in parallel with the capacitive load, a voltage divider is
created, introducing a dc error at the output and slightly
reducing the output swing. The error introduced is proportional to the ratio RS/RL and may be negligible.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. This output stage is
capable of driving 600Ω loads connected to any point
between V+ and ground. For light resistive loads (> 50kΩ),
the output voltage can typically swing to within 1mV from
the supply rail. With moderate resistive loads (2kΩ to
50kΩ), the output can swing to within a few tens of millivolts from the supply rails while maintaining high open-loop
gain. See the typical performance curve “Output Voltage
Swing vs Output Current.”
INPUT PROTECTION
Device inputs are protected by ESD diodes that will conduct
if the input voltages exceed the power supplies by more than
300mV. Momentary voltages greater than 300mV beyond
the power supply can be tolerated if the current on the input
pins is limited to 10mA. This is easily accomplished with an
input resistor as shown in Figure 4. Many input signals are
inherently current-limited to less than 10mA, therefore, a
limiting resistor is not required.
V+
RS
VOUT
OPAx342
10Ω to
20Ω
VIN
CAPACITIVE LOAD AND STABILITY
The OPA342 series op amps in unity-gain configuration can
drive up to 250pF pure capacitive load. Increasing the gain
RL
CL
FIGURE 5. Series Resistor in Unity-Gain Configuration
Improves Capacitive Load Drive.
DESIGN OPTIMIZATION WITH RAIL-TO-RAIL INPUT OP AMPS
In most applications, operation is within the range of only
one differential pair. However, some applications can
subject the amplifier to a common-mode signal in the
transition region. Under this condition, the inherent mismatch between the two differential pairs may lead to
degradation of the CMRR and THD. The unity-gain
buffer configuration is the most problematic—it will
traverse through the transition region if a sufficiently
wide input swing is required. A design option would be
to configure the op amp as a unity-gain inverter as shown
below and hold the noninverting input at a set commonmode voltage outside the transition region. This can be
accomplished with a voltage divider from the supply. The
voltage divider should be designed such that the biasing
point for the noninverting input is outside the transition
the region.
R
R
VOUT
VIN
VCM
FIGURE 3. Design Optimization.
®
9
OPA342, OPA2342, OPA4342
DRIVING A/D CONVERTERS
ture packages of the OPA342, the combination is ideal for
space-limited and low-power applications. In this configuration, an RC network at the A/D’s input can be used to
filter charge injection.
OPA342 series op amps are optimized for driving medium
speed sampling A/D converters. The OPA342 series provides an effective means of buffering the A/D’s input
capacitance and resulting charge injection while providing
signal gain.
Figure 7 shows the OPA2342 driving an ADS7822 in a
speech bandpass filtered data acquisition system. This
small, low-cost solution provides the necessary amplification and signal conditioning to interface directly with an
Electret microphone. This circuit will operate with +2.7V
to +5V at less than 500µA quiescent current.
Figures 6 shows the OPA342 in a basic noninverting
configuration driving the ADS7822. The ADS7822 is
a 12-bit, micro-power sampling converter in the tiny
MSOP-8 package. When used with the low power, minia-
+5V
0.1µF
0.1µF
1 VREF
8 V+
DCLOCK
500Ω
+In
OPA342
ADS7822
12-Bit A/D
2
VIN
DOUT
–In
CS/SHDN
3
3300pF
7
6
Serial
Interface
5
GND 4
VIN = 0V to 5V for
0V to 5V output.
NOTE: A/D Input = 0 to VREF
RC network filters high frequency noise.
FIGURE 6. OPA342 in Noninverting Configuration Driving ADS7822.
V+ = +2.7V to 5V
Passband 300Hz to 3kHz
R9
510kΩ
R1
1.5kΩ
R2
1MΩ
R4
20kΩ
C3
33pF
C1
1000pF
1/2
OPA2342
Electret
Microphone(1)
R3
1MΩ
R6
100kΩ
R7
51kΩ
R8
150kΩ
VREF 1 V+ 8
7
C2
1000pF
1/2
OPA2342
+IN
ADS7822 6
12-Bit A/D
5
2
–IN
3
4
NOTE: (1) Electret microphone
powered by R1.
R5
20kΩ
G = 100
GND
FIGURE 7. Speech Bandpass Filtered Data Acquisition System.
®
OPA342, OPA2342, OPA4342
10
DCLOCK
DOUT
CS/SHDN
Serial
Interface
INFLUENCE OF COMMON-MODE REJECTION ON OFFSET VOLTAGE
The offset voltage (VOS) of the OPA342 is guaranteed
to be within ±6mV over the power supply range 2.7V
to 5.5V with the common-mode voltage at VS/2. This
specification can be combined with the common-mode
rejection ratio specification to determine worst-case
offset under the conditions of a given application.
specified offset measurement configuration, representing a
2.75V variation in common-mode voltage (VS/2 = 2.75V in
the specification versus 0V in the application).
Calculation of the worst-case expected offset would be
as follows:
Worst Case VOS =
Common-Mode Rejection Ratio (CMRR) is specified
in dB, which can be converted to µV/V using the
equation:
CMRR (in V/V) =
10 [(CMRR in dB)/–20]
Maximum specified VOS +
(2)
(common-mode variation • CMRR)
VOSWC =
(1)
6mV +
For the OPA342, the worst-case CMRR at 5.5V supply
over the full common-mode range is 66dB, or approximately 501µV/V. This means that for every volt of
change in common-mode, the offset could shift up to
approximately 501µV.
(2.75V • 501µV/V)
= ±7.38mV
For the OPA342, a specification is also provided for
power supply rejection. This information is useful for
established expected offset variations in applications
with varying supply voltage. Because the OPA342 offset is guaranteed over the full supply range, power
supply rejection errors do not need to be factored into
the worst-case offset analysis.
These numbers can be used to calculate excursions from
the specified offset voltage under different application
conditions. For example, a common application might
configure the amplifier with a +5.5V single supply with
0V common-mode. This configuration varies from the
®
11
OPA342, OPA2342, OPA4342