MAX4453(2001) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX4453
(Rev.:2001)

Low-Cost, +3V/+5V, 620µA, 200MHz, Single-Supply Op Amps with Rail-to-Rail Outputs

Maxim Integrated 

Low-Cost, +3V/+5V, 620µA, 200MHz,

Single-Supply Op Amps with Rail-to-Rail Outputs

Detailed Description

The MAX4452/MAX4352 single, MAX4453/MAX4353

dual, and MAX4454/MAX4354 quad, single-supply, rail-

to-rail, voltage-feedback amplifiers achieve high slew

rates and wide bandwidths while consuming only

620µA per amplifier. Excellent speed/power ratio

makes them ideal for portable devices and high-fre-

quency signal applications.

Internal feedback around the output stage ensures low

open-loop output impedance, reducing gain sensitivity

to load variations. This feedback also produces

demand-driven current bias to the output transistors.

Rail-to-Rail Outputs, Ground-Sensing Input

The input common-mode range extends from (VEE -

0.1V) to (VCC - 1.5V) with excellent common-mode

rejection. Beyond this range, the amplifier output is a

nonlinear function of the input, but does not undergo

phase reversal or latchup.

The output swings to within 180mV of either power-sup-

ply rail with a 1kΩ load. The input ground-sensing and

the rail-to-rail output substantially increase the dynamic

range.

Output Capacitive Loading and Stability

The MAX4452/MAX4453/MAX4454/MAX4352/MAX4353/

MAX4354 are optimized for AC performance. They are

not designed to drive highly reactive loads. Such loads

decrease phase margin and may produce excessive

ringing and oscillation. The use of an isolation resistor

eliminates this problem (Figure 1). Figure 2 is a graph

of the Optimal Isolation Resistor (RISO) vs. Capacitive

Load.

Applications Information

Choosing Resistor Values

Unity-Gain Configuration

The MAX4452/MAX4453/MAX4454 are internally com-

pensated for unity gain. When configured for unity gain,

a 24Ω feedback resistor (RF) is recommended. This

resistor improves AC response by reducing the Q of

the parallel LC circuit formed by the parasitic feedback

capacitance and inductance.

Inverting and Noninverting Configurations

Select the gain-setting feedback (RF) and input (RG)

resistor values that best fit the application. Large resis-

tor values increase voltage noise and interact with the

amplifier’s input and PC board capacitance. This can

generate undesirable poles and zeros and decrease

bandwidth or cause oscillations. For example, a nonin-

verting gain-of-two configuration (RF = RG) using 1kΩ

resistors, combined with 2pF of amplifier input capaci-

tance and 1pF of PC board capacitance, causes a pole

at 106MHz. Since this pole is within the amplifier band-

width, it jeopardizes stability. Reducing the 1kΩ resis-

tors to 100Ω extends the pole frequency to 1.06GHz,

but could limit output swing by adding 200Ω in parallel

with the amplifier’s load resistor.

Note: For high-gain applications where output offset

voltage is a consideration, choose RS to be equal to

the parallel combination of RF and RG (Figures 3a and

3b).

3b):

RS

=

RF × RG

RF + RG

RG

RF

VIN

RBIN

RISO

VOUT

CL

Figure 1. Driving a Capacitive Load Through an Isolation

Resistor

ISOLATION RESISTANCE

vs. CAPACITIVE LOAD

30

28

26

24

22

20

18

16

14

12

10

0

50

100

150

CLOAD (pF)

Figure 2. Optimal Isolation Resistor vs. Capacitive Load

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