ALD4704A/ALD4704B

Advanced Linear Devices

4 of 9

ALD4704

±7

±6

±5

TYPICAL PERFORMANCE CHARACTERISTICS

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

Design & Operating Notes:

1. The ALD4704A/ALD4704B/ALD4704 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 ALD4704A/ALD4704B/

ALD4704 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

ALD4704A/ALD4704B/ALD4704 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 ALD4704A/ALD4704B/

ALD4704 is much more resistant to parasitic oscillations.

2. The ALD4704A/ALD4704B/ALD4704 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 ALD4704A/ALD4704B/ALD4704 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 neces-

sary 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 ALD4704A/ALD4704B/ALD4704 an effective analog sig-

nal buffer for medium to high source impedance sensors, transducers,

and other circuit networks.

5. The ALD4704A/ALD4704B/ALD4704 operational amplifier has been

designed with static discharge protection and 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 accept-

able levels while causing very small or negligible accuracy effects.