ALD1701A/ALD1701B

Advanced Linear Devices

4 of 9

ALD1701/ALD1701G

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

OPEN LOOP VOLTAGE GAIN AS A

FUNCTION OF LOAD RESISTANCE

10M

LOAD RESISTANCE (Ω)

10K

100K

1M

1000

100

10

1

Design & Operating Notes:

1. The ALD1701A/ALD1701B/ALD1701/ALD1701G 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 ALD1701A/ALD1701B/

ALD1701/ALD1701G 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 characteris-

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

unity gain frequency.

2. The ALD1701A/ALD1701B/ALD1701/ALD1701G has complemen-

tary 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 compatibility with other operational ampli-

fiers, this switching point has been selected to be about 1.5V below

the positive supply voltage. Since offset voltage trimming on the

ALD1701A/ALD1701B/ALD1701/ALD1701G 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

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 ALD1701A/ALD1701B/ALD1701/ALD1701G operational ampli-

fier 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 not to

exceed 0.3V of the power supply voltage levels.

6. The

ALD1701A/ALD1701B/ALD1701/ALD1701G,

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 0.1°C above ambient

temperature under most operating conditions.

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

SUPPLY CURRENT AS A FUNCTION

OF SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

400

200

300

0

100

0

±1

±2

±3

±4

±5

±6

+25°C

+70°C

+125°C

INPUTS GROUNDED

OUTPUT UNLOADED

-25°C