Low-Cost, High-Speed, Single-Supply, Gain of +2
Buffers with Rail-to-Rail Outputs in SOT23
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 500Ω 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-
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.
These devices operate from a single +3.15V to +11V
power supply or from dual supplies of ±1.575V to
±5.5V. For single-supply operation, bypass the V
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 500Ω input imped-
ance, terminate the input with a 56Ω resistor when the
device is configured for an inverting gain in 50Ω appli-
cations (terminate with 88Ω in 75Ω applications).
Terminate the input with a 49.9Ω resistor in the nonin-
verting case. Output terminating resistors should direct-
ly match cable impedances in either configuration.
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
• 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.