Rail-to-Rail Output Stage

The MAX4198/MAX4199 output stage incorporates a

common-source rail-to-rail structure which maximizes the

dynamic range of the differential amplifier. The output

can swing to within 100mV from each rail with a 5k

Ω load

Shutdown Mode

The MAX4198/MAX4199 have an active-low shutdown

input. SHDN input logic thresholds are referenced to

rail places the amplifiers in a 12µA (max) shutdown

mode. The MAX4198/MAX4199 exit or enter shutdown

in 35µs. In shutdown, the OUT pin is high-impedance.

Applications Information

Driving Capacitive Loads

The MAX4198/MAX4199 are relatively immune to oscilla-

tions caused when driving large capacitive loads.

Although heavy load capacitance increases transient ring-

ing, sustained oscillations typically don’t occur for loads

under 600pF (see Pulse Response with Capacitive Load

in the

Typical Operating Characteristics). Applications that

require driving higher capacitive loads can isolate the out-

put capacitance using a 15

Ω to 100Ω resistor between the

amplifier output and the load (Figure 1). Although adding

an isolation resistor dampens the response enough to pre-

vent oscillations, it does so at the expense of bandwidth

and DC accuracy.

Power Supply Considerations

The MAX4198/MAX4199 operate from single +2.7V to

+7.5V supplies or from dual ±1.35V to ±3.75V supplies,

and they consume only 45µA of supply current.

Excellent power-supply rejection permits the amplifiers

to be operated directly from a decaying 3V cell without

excessive error. To maximize AC performance, the sup-

ply must be bypassed with a 0.1µF ceramic capacitor

to ground that must be as close as possible to the pin.

If dual supplies are used, bypass both supply pins with

0.1µF to ground.

Application Circuits

Differential amplifiers can be used in single-ended and

other amplifier applications. Figures 2 through 6 show

the MAX4198/MAX4199 in different configurations. The

internally trimmed and matched resistors offer conven-

ience and have a distinct advantage over external

resistors. These amplifiers are not compensated for sin-

gle-ended unity gain; therefore, IN- should not be con-

nected to OUT or left unconnected.

Micropower, Single-Supply, Rail-to-Rail

Precision Differential Amplifiers

10

______________________________________________________________________________________

MAX4198

MAX4199

FB

OUT

INPUT

IN+

IN-

REF

OUTPUT

Figure 1. Dual-Supply, Capacitive-Load Driving Circuit

MAX4198

MAX4199

FB

OUT

IN+

IN-

REF

(MAX4198)

(MAX4199)

Figure 2. Standard Difference Amplifier

MAX4198

MAX4199

FB

OUT

IN+

IN-

REF

Figure 3. Precision Inverting Buffer