Low-Cost, High-Speed, Single-Supply, Gain of +2

Buffers with Rail-to-Rail Outputs in SOT23

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9

Input Voltage Range and Output Swing

The input range for the MAX4014 family extends from

increases the dynamic range for single-supply applica-

tions. The outputs drive a 2k

Ω load to within 60mV of

the power-suply rails. With heavier loads, the output

swing is reduced as shown in the

Electrical Character-

istics and the Typical Operating Characteristics. As the

load increases, the input range is effectively limited by

the output-drive capability, since the buffers have a

fixed voltage gain of +2 or -1.

For example, a 50

Ω load can typically be driven from

when operating from a single +5V supply. If the buffer is

operated in the noninverting, gain of +2 configuration

with the inverting input grounded, the effective input

voltage range becomes 20mV to 1.7V, instead of the

-100mV to 2.75V indicated by the

Electrical Character-

istics. Beyond the effective input range, the buffer out-

put is a nonlinear function of the input, but it will not

undergo phase reversal or latchup.

Enable

The MAX4019 has an enable feature (EN_) that allows

the buffer to be placed in a low-power state. When the

buffers are disabled, the supply current will not exceed

550µA per buffer.

As the voltage at the EN_ pin approaches the negative

supply rail, the EN_ input current rises. Figure 2 shows

a graph of EN_ input current versus EN_ pin voltage.

Figure 3 shows the addition of an optional resistor in

series with the EN pin, to limit the magnitude of the cur-

rent increase. Figure 4 displays the resulting EN pin

input current to voltage relationship.

20

-160

0

100

300

500

-100

-120

0

200

400

-60

-140

-20

-40

-80

Figure 2. Enable Logic-Low Input Current vs. Enable Logic-

Low Threshold

OUT

IN-

EN_

IN+

10k

ENABLE

MAX40_ _

500

Ω

500

Ω

Figure 3. Circuit to Reduce Enable Logic-Low Input Current

0

-10

0

100

300

500

-7

-8

-1

200

400

-3

-5

-9

-2

-4

-6

Figure 4. Enable Logic-Low Input Current vs. Enable Logic-

Low Threshold with 10k

Ω Series Resistor