ALD4702A/ALD4702B

Advanced Linear Devices

4 of 9

ALD4702

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)

12

10

8

6

2

4

0

±6

±5

±4

±3

±1

±2

INPUTS GROUNDED

OUTPUTS UNLOADED

-25°C

+80°C

+125°C

+25°C

Design & Operating Notes:

1. The ALD4702A/ALD4702B/ALD4702 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 ALD4702A/ALD4702B/ALD4702 is

internally compensated for unity gain stability using a novel scheme.

This design produces a clean single pole roll off in the gain character-

istics while providing for more than 70 degrees of phase margin at the

unity gain frequency.

A unity gain buffer using the ALD4702A/

ALD4702B/ALD4702 will typically drive 400pF of external load capaci-

tance without stability problems. In the inverting unity gain configura-

tion, it can drive up to 800pF of load capacitance. Compared to other

CMOS operational amplifiers, the ALD4702A/ALD4702B/ALD4702 is

much more resistant to parasitic oscillations.

2. The ALD4702A/ALD4702B/ALD4702 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 selected

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

trimming on the ALD4702A/ALD4702B/ALD4702 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 ALD4702A/ALD4702B/

ALD4702 an effective analog signal buffer for medium to high

source impedance sensors, transducers, and other circuit net-

works.

5. The ALD4702A/ALD4702B/ALD4702 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 accu-

racy effects.