value, based on driving the output voltage to within

50mV, 100mV, and 200mV of either power-supply rail.

For example, a MAX4241 running from a single +1.8V

Ω

The same application can drive a 3.3k

Ω load resistor

Driving Capacitive Loads

The MAX4240–MAX4244 are unity-gain stable for loads

up to 200pF (see Load Resistor vs. Capacitive Load

graph in

Typical Operating Characteristics). Applica-

tions that require greater capacitive drive capability

should use an isolation resistor between the output and

the capacitive load (Figure 8). Note that this alternative

voltage divider with the load resistor.

Power-Supply Bypassing and Layout

The MAX4240–MAX4244 family operates from either a

single +1.8V to +5.5V supply or dual ±0.9V to ±2.75V

supplies. For single-supply operation, bypass the

separate 100nF capacitors.

Good PC board layout techniques optimize perfor-

mance by decreasing the amount of stray capacitance

at the op amp’s inputs and output. To decrease stray

capacitance, minimize trace lengths by placing exter-

nal components as close as possible to the op amp.

Surface-mount components are an excellent choice.

R

=

1.8V - 0.1V

240 A

7k

to V

L

EE

µ

=

Ω

Single/Dual/Quad, +1.8V/10µA, SOT23,

Beyond-the-Rails Op Amps

______________________________________________________________________________________

13

MAX4240

MAX4241

MAX4242

MAX4243

MAX4244

≈ 1

Figure 8a Using a Resistor to Isolate a Capacitive Load from

the Op Amp

50mV/div

IN

OUT

50mV/div

MAX4240-44 fig08b

100

µs/div

Figure 8b. Pulse Response without Isolating Resistor

50mV/div

IN

OUT

50mV/div

MAX4240-44 fig08c

100

µs/div

Figure 8c. Pulse Response with Isolating Resistor