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

Buffers with Rail-to-Rail Outputs in SOT23

8

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_______________Detailed Description

The MAX4014/MAX4017/MAX4019/MAX4022 are sin-

gle-supply, rail-to-rail output, voltage-feedback, closed-

loop buffers that employ current-feedback techniques

to achieve 600V/µs slew rates and 200MHz band-

widths. These buffers use internal 500

Ω resistors to

provide a preset closed-loop gain of +2V/V in the non-

inverting configuration or -1V/V in the inverting configu-

ration. Excellent harmonic distortion and differential

gain/phase performance make these buffers an ideal

choice for a wide variety of video and RF signal-pro-

cessing applications.

Local feedback around the buffer’ s output stage

ensures low output impedance, which reduces gain

sensitivity to load variations. This feedback also pro-

duces demand-driven current bias to the output tran-

sistors for ±120mA drive capability, while constraining

total supply current to less than 7mA.

__________Applications Information

Power Supplies

These devices operate from a single +3.15V to +11V

power supply or from dual supplies of ±1.575V to

to ground with a 0.1µF capacitor as close to the pin as

possible. If operating with dual supplies, bypass each

supply with a 0.1µF capacitor.

Selecting Gain Configuration

Each buffer in the MAX4014 family can be configured

for a voltage gain of +2V/V or -1V/V. For a gain of

+2V/V, ground the inverting terminal. Use the noninvert-

ing terminal as the signal input of the buffer (Figure 1a).

Grounding the noninverting terminal and using the

inverting terminal as the signal input configures the

buffer for a gain of -1V/V (Figure 1b).

Since the inverting input exhibits a 500

Ω input imped-

ance, terminate the input with a 56

Ω resistor when the

device is configured for an inverting gain in 50

Ω appli-

cations (terminate with 88

Ω in 75Ω applications).

Terminate the input with a 49.9

Ω resistor in the nonin-

verting case. Output terminating resistors should direct-

ly match cable impedances in either configuration.

Layout Techniques

Maxim recommends using microstrip and stripline tech-

niques to obtain full bandwidth. To ensure that the PC

board does not degrade the buffer’s performance, design

it for a frequency greater than 1GHz. Pay careful attention

to inputs and outputs to avoid large parasitic capaci-

tance. Whether or not you use a constant-impedance

board, observe the following guidelines when designing

the board:

• Don’t use wire-wrapped boards. They are too inductive.

• Don’t use IC sockets. They increase parasitic capac-

itance and inductance.

• Use surface-mount instead of through-hole compon-

ents for better high-frequency performance.

• Use a PC board with at least two layers; it should be

as free from voids as possible.

• Keep signal lines as short and as straight as possi-

ble. Do not make 90° turns; round all corners.

MAX40_ _

500

Ω

500

Ω

IN-

OUT

*R

*R

OUT

IN

IN+

MAX40_ _

500

Ω

500

Ω

OUT

*R

*R

OUT

IN+

IN-

IN