MAX9944(2009) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX9944
(Rev.:2009)

High-Voltage, Precision, Low-Power Op Amps

Maxim Integrated 

High-Voltage, Precision, Low-Power Op Amps

MAX9943

6 TDFN-EP

1

—

—

2

3

—

—

4

—

—

5

6

MAX9943

8 µMAX

6

—

—

4

3

—

—

2

—

—

1, 5, 8

7

MAX9944

8 SO/TDFN-EP

—

1

7

4

—

3

5

—

2

6

—

8

—

—

—

Pin Description

NAME

FUNCTION

OUT

OUTA

OUTB

VEE

IN+

INA+

INB+

IN-

INA-

INB-

N.C.

VCC

EP

Output

Output A

Output B

Negative Power Supply. Bypass with a 0.1µF capacitor to ground.

Positive Input

Positive Input A

Positive Input B

Negative Input

Negative Input A

Negative Input B

No Connection

Positive Power Supply. Bypass with a 0.1µF capacitor to ground.

Exposed Pad (TDFN Only). Connect to a large ground plane to

maximize thermal performance. Not intended as an electrical

connection point.

Detailed Description

The MAX9943/MAX9944 are single/dual operational

amplifiers designed for industrial applications. They

operate from 6V to 38V supply range while maintaining

excellent performance. These devices utilize a three-

stage architecture optimized for low offset voltage and

low input noise with only 550µA supply current. The

devices are unity gain stable with a 1nF capacitive

load. These well-matched devices guarantee the high

open-loop gain, CMRR, PSRR, and low voltage offset.

The MAX9943/MAX9944 provide a wide input/output

voltage range. The input terminals of the MAX9943/

MAX9944 are protected from excessive differential volt-

age with back-to-back diodes. The input signal current

is also limited by an internal series resistor. With a 40V

differential voltage, the input current is limited to 20mA.

The output can swing to the negative rail while deliver-

ing 20mA of current, which is ideal for loop-powered

system applications. The specifications and operation

of the MAX9943/MAX9944 family is guaranteed over the

-40°C to +125°C temperature range.

Application Information

Bias Current vs. Input Common Mode

The MAX9943/MAX9944 use an internal bias current

cancellation circuit to achieve very low bias current over

a wide input common-mode range. For such a circuit to

function properly, the input common mode must be at

least 300mV away from the negative supply VEE. The

input common mode can reach the negative supply

VEE. However, in the region between VEE and VEE +

0.3V, there is an increase in bias current for both inputs.

Capacitive Load Stability

Driving large capacitive loads can cause instability in

many op amps. The MAX9943/MAX9944 are stable with

capacitive loads up to 1nF. The Capacitive Load vs.

Resistive Load graph in the Typical Operating

Characteristics gives the stable operation region for

capacitive versus resistive loads. Stability with higher

capacitive loads can be improved by adding an isola-

tion resistor in series with the op-amp output, as shown

in Figure 1. This resistor improves the circuit’s phase

margin by isolating the load capacitor from the amplifi-

er’s output.

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