ALD2704A/ALD2704B

Advanced Linear Devices

4 of 9

ALD2704

TYPICAL PERFORMANCE CHARACTERISTICS

Design & Operating Notes:

1. The ALD2704A/ALD2704B/ALD2704 CMOS operational amplifier

uses a 3 gain stage architecture and an improved frequency compen-

sation scheme to achieve large voltage gain, high output driving

capability, and better frequency stability. The ALD2704A/ALD2704B/

ALD2704 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

ALD2704A/ALD2704B/ALD2704 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 ALD2704A/ALD2704B/

ALD2704 is much more resistant to parasitic oscillations.

2. The ALD2704A/ALD2704B/ALD2704 has complementary p-channel

and n-channel input differential stages connected in parallel to accom-

plish 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 se-

lected to be about 1.5V above the negative supply voltage. As offset

voltage trimming on the ALD2704A/ALD2704B/ALD2704 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 (10V 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. The

voltage follower configuration, the oscillation and resistant with the rail-

to-rail input and output feature, makes the ALD2704A/ALD2704B/

ALD2704 an effective analog signal buffer for medium to high source

impedance sensors, transducers, and other circuit networks.

5. The ALD2704A/ALD2704B/ALD2704 operational amplifier has been

designed to provide 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.

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

COMMON MODE INPUT VOLTAGE RANGE

AS A FUNCTION OF SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

±7

±6

±5

±4

±3

±2

±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

SUPPLY CURRENT AS A FUNCTION

OF SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

0

0

±1

±2

±3

±4

±5

±6

INPUTS GROUNDED

OUTPUT UNLOADED

+80°C

+25°C

-25°C

±7

1

2

3

4

5

6

7

8

+125°C