ALD2702A/ALD2702B

Advanced Linear Devices

4 of 9

ALD2702

TYPICAL PERFORMANCE CHARACTERISTICS

COMMON MODE INPUT VOLTAGE RANGE

AS A FUNCTION OF SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

±7

±6

±5

±4

±3

±2

±1

0

0

±1

±2

±3

±4

±5

±6

±7

OPEN LOOP VOLTAGE GAIN AS A FUNCTION

OF SUPPLY VOLTAGE AND TEMPERATURE

SUPPLY VOLTAGE (V)

1000

100

10

1

0

±2

±4

±6

±8

INPUT BIAS CURRENT AS A FUNCTION

OF AMBIENT TEMPERATURE

AMBIENT TEMPERATURE (°C)

1000

100

10

0.1

1.0

100

-25

0

75

125

50

25

-50

10000

SUPPLY CURRENT AS A FUNCTION

OF SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

6

5

4

3

1

2

0

±6

±5

±4

±3

±1

±2

INPUTS GROUNDED

OUTPUTS UNLOADED

-25°C

+80°C

+125°C

+25°C

Design & Operating Notes:

1. The ALD2702A/ALD2702B/ALD2702 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. The ALD2702A/

ALD2702B/ALD2702 is internally compensated for unity gain

stability using a novel scheme. This design 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.

A unity gain buffer using the ALD2702A/ALD2702B/ALD2702 will

typically drive 400pF of external load capacitance without stability

problems. In the inverting unity gain configuration, it can drive up

to 800pF of load capacitance.

Compared to other CMOS

operational amplifiers, the ALD2702A/ALD2702B/ALD2702 has

shown itself to be more resistant to parasitic oscillations.

2. The ALD2702A/ALD2702B/ALD2702 has complementary p-channel

and n-channel input differential stages connected in parallel to

accomplish rail-to-rail input common mode voltage range. With the

common mode input voltage close to the power supplies, one of the

two differential stages is switched off internally.

To maintain

compatibility with other operational amplifiers, this switching point

has been selected to be about 1.5V above the negative supply voltage.

As offset voltage trimming on the ALD2702A/ALD2702B/ALD2702

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

greater than 2.5 (5V operation), where the common mode voltage

does not make excursions below this switching point.

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. 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 the ALD2702A/ALD2702B/ALD2702 an effective analog signal

buffer for medium to high source impedance sensors, transducers,

and other circuit networks.

5. The ALD2702A/ALD2702B/ALD2702 operational amplifier has been

designed with 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.

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. Alternatively, a 100KΩ or higher value resistor at the input

terminals will limit input currents to acceptable levels while causing

very small or negligible accuracy effects.