A
DVANCED
L
INEAR
D
EVICES,
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NC.
ALD2701A/ALD2701B
ALD2701
DUAL MICROPOWER RAIL-TO-RAIL CMOS OPERATIONAL AMPLIFIER
GENERAL DESCRIPTION
The ALD2701 is a dual monolithic CMOS micropower high slew rate
operational amplifier intended for a broad range of analog applications
using
±1V
to
±6V
dual power supply systems, as well as +2V to +12V
battery operated systems. All device characteristics are specified for +5V
single supply or
±2.5V
dual supply systems. Supply current is 500µA
maximum at 5V supply voltage. It is manufactured with Advanced Linear
Devices' enhanced ACMOS silicon gate CMOS process.
The ALD2701 is designed to offer a trade-off of performance parameters
providing a wide range of desired specifications. It offers the popular
industry standard pin configuration of
µA747
and ICL7621 types.
The ALD2701 has been developed specifically for the +5V single supply or
±1V
to
±6V
dual supply user. Several important characteristics of the
device make application easier to implement at those voltages.
First, each operational amplifier can operate with rail-to-rail input and
output voltages. This means the signal input voltage and output voltage
can be equal to the positive and negative supply voltages. This feature
allows numerous analog serial stages and flexibility in input signal bias
levels. Secondly, each device was designed to accommodate mixed
applications where digital and analog circuits may operate off the same
power supply or battery. Thirdly, the output stage can typically drive up to
50pF capacitive and 10KΩ resistive loads.
These features, combined with extremely low input currents, high open
loop voltage gain of 100V/mV, useful bandwidth of 700KHz, a slew rate of
0.7V/µs, low power dissipation of 0.5mW, low offset voltage and temperature
drift, make the ALD2701 a versatile, micropower dual operational amplifier.
The ALD2701, designed and fabricated with silicon gate CMOS technology,
offers 1pA typical input bias current. On chip offset voltage trimming allows
the device to be used without nulling in most applications.
Due to low voltage and low power operation, reliability and operating
characteristics, such as input bias currents and warm up time, are greatly
improved.
ORDERING INFORMATION
Operating Temperature Range
-55°C to +125°C
0°C to +70°C
0°C to +70°C
8-Pin
CERDIP
Package
ALD 2701A DA
ALD 2701B DA
ALD 2701 DA
8-Pin
Small Outline
Package (SOIC)
ALD 2701A SA
ALD 2701B SA
ALD 2701 SA
8-Pin
Plastic Dip
Package
ALD 2701A PA
ALD 2701B PA
ALD 2701 PA
FEATURES
• All parameters specified for +5V single
supply or
±2.5V
dual supply systems
• Rail to rail input and output voltage ranges
• Unity gain stable
• Extremely low input bias currents -- 1.0pA
• High source impedance applications
• Dual power supply
±1.0V
to
±6.0V
• Single power supply +2V to +12V
• High voltage gain
• Output short circuit protected
• Unity gain bandwidth of 0.7MHz
• Slew rate of 0.7V/µs
• Low power dissipation
• Symmetrical output drive
APPLICATIONS
•
•
•
•
•
•
•
•
•
•
•
•
Voltage follower/buffer/amplifier
Charge integrator
Photodiode amplifier
Data acquisition systems
High performance portable instruments
Signal conditioning circuits
Sensor and transducer amplifiers
Low leakage amplifiers
Active filters
Sample/Hold amplifier
Picoammeter
Current to voltage converter
PIN CONFIGURATION
OUT
A
-IN
A
+IN
A
V-
1
2
3
4
TOP VIEW
DA, PA, SA PACKAGE
8
7
6
5
V+
OUT
B
-IN
B
+IN
B
* Contact factory for industrial temperature range
© 1998 Advanced Linear Devices, Inc. 415 Tasman Drive, Sunnyvale, California 94089 -1706 Tel: (408) 747-1155 Fax: (408) 747-1286 http://www.aldinc.com
Design & Operating Notes:
1. The ALD2701 CMOS operational amplifier uses a 3 gain stage
architecture and an improved frequency compensation scheme to
achieve large voltage gain, high output driving capability, and better
frequency stability. In a conventional CMOS operational amplifier
design, compensation is achieved with a pole splitting capacitor
together with a nulling resistor. This method is, however, very bias
dependent and thus cannot accommodate the large range of supply
voltage operation as is required from a stand alone CMOS operational
amplifier. The ALD2701 is internally compensated for unity gain
stability using a novel scheme that does not use a nulling resistor. This
scheme produces a clean single pole roll off in the gain characteristics
while providing for more than 70 degrees of phase margin at the unity
gain frequency.
2. The ALD2701 has complementary p-channel and n-channel input
differential stages connected in parallel to accomplish rail to rail input
common mode voltage range. This means that with the ranges of
common mode input voltage close to the power supplies, one of the
two differential stages is switched off internally. To maintain com-
patibility with other operational amplifiers, this switching point has
been selected to be about 1.5V below the positive supply voltage.
Since offset voltage trimming on the ALD2701 is made when the input
voltage is symmetrical to the supply voltages, this internal switching
does not affect a large variety of applications such as an inverting
amplifier or non-inverting amplifier with a gain larger than 2.5 (5V
operation), where the common mode voltage does not make excur-
sions above this switching point. The user should however, be aware
that this switching does take place if the operational amplifier is
connected as a unity gain buffer, and should make provision in his
design to allow for input offset voltage variations.
3. The input bias and offset currents are essentially input protection
diode reverse bias leakage currents, and are typically less than 1pA
at room temperature. This low input bias current assures that the
analog signal from the source will not be distorted by input bias
currents. Normally, this extremely high input impedance of greater
than 10
12
Ω
would not be a problem as the source impedance would
limit the node impedance. However, for applications where source
impedance is very high, it may be necessary to limit noise and hum
pickup through proper shielding.
4. The output stage consists of class AB complementary output drivers,
capable of driving a low resistance load. The output voltage swing is
limited by the drain to source on-resistance of the output transistors as
determined by the bias circuitry, and the value of the load resistor.
When connected in the voltage follower configuration, the oscillation
resistant feature, combined with the rail to rail input and output feature,
makes an effective analog signal buffer for medium to high source
impedance sensors, transducers, and other circuit networks.
5. The ALD2701 operational amplifier has been designed to provide full
static discharge protection. Internally, the design has been carefully
implemented to minimize latch up. However, care must be exercised
when handling the device to avoid strong static fields that may
degrade a diode junction, causing increased input leakage currents.
In using the operational amplifier, the user is advised to power up the
circuit before, or simultaneously with, any input voltages applied and
to limit input voltages not to exceed 0.3V of the power supply voltage
levels.
6. The ALD2701, with its micropower operation, offers numerous benefits
in reduced power supply requirements, less noise coupling and
current spikes, less thermally induced drift, better overall reliability
due to lower self heating, and lower input bias current. It requires
practically no warm up time as the chip junction heats up to only 0.2°C
above ambient temperature under most operating conditions.
TYPICAL PERFORMANCE CHARACTERISTICS
SUPPLY CURRENT AS A FUNCTION
OF SUPPLY VOLTAGE
INPUTS GROUNDED
OUTPUT UNLOADED
T
A
= -55°C
±600
±400
+70°C
±200
0
0
±1
±2
±3
±4
±5
±6
SUPPLY VOLTAGE (V)
+125°C
+25°C
-25°C
COMMON MODE INPUT VOLTAGE RANGE
AS A FUNCTION OF SUPPLY VOLTAGE
±7
±6
COMMON MODE INPUT
VOLTAGE RANGE (V)
SUPPLY CURRENT (µA)
±800
T
A
= 25°C
±5
±4
±3
±2
±1
0
0
±1
±2
±3
±4
±5
±6
±7
SUPPLY VOLTAGE (V)
OPEN LOOP VOLTAGE GAIN AS A
FUNCTION OF LOAD RESISTANCE
1000
10000
INPUT BIAS CURRENT AS A FUNCTION
OF AMBIENT TEMPERATURE
INPUT BIAS CURRENT (pA)
OPEN LOOP VOLTAGE
GAIN (V/mV)
1000
100
V
S
=
±2.5V
100
10
10
V
S
=
±2.5V
T
A
= 25°C
1
10K
100K
1M
10M
1.0
0.1
-50
-25
0
25
50
75
100
125
LOAD RESISTANCE (Ω)
AMBIENT TEMPERATURE (°C)
ALD2701A/ALD2701B
ALD2701
Advanced Linear Devices
4
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