Detailed description, Pin description, Rail-to-rail input stage – Rainbow Electronics MAX4040_MAX4044 User Manual

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MAX4040–MAX4044

Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps

_______________________________________________________________________________________

_______________Detailed Description

Rail-to-Rail Input Stage

The MAX4040–MAX4044 have rail-to-rail inputs and
rail-to-rail output stages that are specifically designed
for low-voltage, single-supply operation. The input
stage consists of separate NPN and PNP differential
stages, which operate together to provide a common-
mode range extending to both supply rails. The
crossover region of these two pairs occurs halfway
between V

and V

. The input offset voltage is typi-

cally 200µV. Low operating supply voltage, low supply
current, rail-to-rail common-mode input range, and rail-
to-rail outputs make this family of operational amplifiers

an excellent choice for precision or general-purpose,
low-voltage battery-powered systems.

Since the input stage consists of NPN and PNP pairs,
the input bias current changes polarity as the common-
mode voltage passes through the crossover region.
Match the effective impedance seen by each input to
reduce the offset error caused by input bias currents
flowing through external source impedances (Figures
1a and 1b). The combination of high source impedance
plus input capacitance (amplifier input capacitance
plus stray capacitance) creates a parasitic pole that
produces an underdamped signal response. Reducing
input capacitance or placing a small capacitor across
the feedback resistor improves response in this case.

______________________________________________________________Pin Description

—

Negative Supply. Tie to ground for
single-supply operation.

—

Amplifier Output. High impedance
when in shutdown mode.

OUT

—

Inverting Input

IN-

Noninverting Input

IN+

—

5, 7,

8, 10

—

No Connection. Not internally con-
nected.

N.C.

—

Positive Supply

—

1, 9

1, 7

1, 13

1, 7

Outputs for Amplifiers A and B. High
impedance when in shutdown mode.

OUTA,

OUTB

Shutdown Input. Drive high, or tie to
V

for normal operation. Drive to V

to place device in shutdown mode.

SHDN

—

2, 8

2, 6

2, 12

2, 6

—

3, 7

3, 5

3, 11

3, 5

Noninverting Inputs to Amplifiers A
and B

INA+,

INB+

—

5, 6

Inverting Inputs to Amplifiers A and B

INA-,

INB-

—

6, 9

—

8, 14

Outputs for Amplifiers C and D

OUTC,

OUTD

Shutdown Inputs for Amplifiers A
and B. Drive high, or tie to V

for

normal operation. Drive to V

place device in shutdown mode.

SHDNA,

SHDNB

—

9, 13

—

10, 12

Noninverting Inputs to Amplifiers C
and D

INC+,

IND+

Inverting Inputs to Amplifiers C and D

INC-,

IND-

1, 5

—

1, 5, 8

—

MAX4043

MAX4044

PIN

µMAX

MAX4042

MAX4041

FUNCTION

NAME

SOT23-5

MAX4040

SO/µMAX