A
DVANCED
L
INEAR
D
EVICES,
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NC.
ALD2711A/ALD2711B
ALD2711
DUAL MICROPOWER PRECISION RAIL-TO-RAIL CMOS OPERATIONAL AMPLIFIER
GENERAL DESCRIPTION
The ALD2711 is a dual monolithic CMOS micropower precision 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. Typical
supply current is 200µA at 5V supply voltage. It is manufactured with
Advanced Linear Devices' enhanced ACMOS silicon gate CMOS
process.
The device has an input stage that operates to +300mV above and
-300mV below the supply voltages with no adverse effects and/or
phase reversals.
The ALD2711 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 at 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, high useful bandwidth, and slew rate make the
ALD2711 a versatile, micropower operational amplifier.
The ALD2711 with on-chip offset voltage trimming allows the device to
be used without nulling in most applications. The unique characteristics
of the ALD2711 are modeled in an available macromodel.
FEATURES
• Designed and characterized for 5V operation
• Linear mode operation with input voltages
300mV beyond supply rails
• Output voltages to within 2mV of power supply
rails when driving a high impedance load
• Unity gain stable
• Extremely low input bias currents -- 0.01pA
• 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 complementary 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
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 2711A DA
ALD 2711B DA
ALD 2711 DA
8-Pin
Small Outline
Package (SOIC)
ALD 2711A SA
ALD 2711B SA
ALD 2711 SA
8-Pin
Plastic Dip
Package
ALD 2711A PA
ALD 2711B PA
ALD 2711 PA
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 ALD2711 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 ALD2711 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 ALD2711 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 ALD2711 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 ALD2711 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 to not exceed 0.3V of the power supply voltage levels.
6. The ALD2711, 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
400
300
+70°C
200
0
0
±1
±2
±3
±4
SUPPLY VOLTAGE (V)
±5
±6
+125°C
+25°C
-25°C
±7
±6
T
A
= 25°C
COMMON MODE INPUT VOLTAGE RANGE
AS A FUNCTION OF SUPPLY VOLTAGE
SUPPLY CURRENT (µA)
500
COMMON MODE INPUT
VOLTAGE RANGE (V)
±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
INPUT BIAS CURRENT AS A FUNCTION
OF AMBIENT TEMPERATURE
1000
INPUT BIAS CURRENT (pA)
OPEN LOOP VOLTAGE
GAIN (V/mV)
100
10
V
S
=
±2.5V
100
1.0
10
V
S
=
±2.5V
T
A
= 25°C
1
10K
100K
1M
10M
0.1
0.01
-50
-25
0
25
50
75
100
125
LOAD RESISTANCE (Ω)
AMBIENT TEMPERATURE (°C)
ALD2711A/ALD2711B
ALD2711
Advanced Linear Devices
4
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