Analog Devices recommends using microstrip and strip-

line techniques to obtain full bandwidth. To ensure that

the PC board does not degrade the amplifier’s perfor-

mance, design it for a frequency greater than 1GHz.

Pay careful attention to inputs and outputs to avoid large

parasitic capacitance. Whether or not you use a constant-

impedance board, observe the following guidelines when

designing the board:

● Don’t use wire-wrap boards because they are too

inductive.

● Don’t use IC sockets because they increase parasitic

capacitance and inductance.

● Use surface-mount instead of through-hole compo-

nents 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 possible.

Do not make 90° turns; round all corners.

Rail-to-Rail Outputs,

Ground-Sensing Input

The input common-mode range extends from (VEE -

200mV) to (VCC - 2.25V) with excellent common-mode

rejection. Beyond this range, the amplifier output is a non-

linear function of the input, but does not undergo phase

reversal or latchup.

The output swings to within 60mV of either power-supply

rail with a 2kΩ load. The input ground-sensing and

the rail-to-rail output substantially increase the dynamic

range. With a symmetric input in a single 5V application,

the input can swing 2.95VP-P, and the output can swing

4.9VP-P with minimal distortion.

Enable Input and Disabled Output

The enable feature (EN_) allows the amplifier to be placed

in a low-power, high-output-impedance state. Typically,

the EN_ logic low input current (IIL) is small. However, as

the EN voltage (VIL) approaches the negative supply rail,

IIL increases (Figure 2). A single resistor connected as

shown in Figure 3 prevents the rise in the logic-low input

current. This resistor provides a feedback mechanism that

increases VIL as the logic input is brought to VEE. Figure

4 shows the resulting input current (IIL).

When the MAX4018 is disabled, the amplifier’s output

impedance is 35kΩ. This high resistance and the low

2pF output capacitance make this part ideal in RF/video

multiplexer or switch applications. For larger arrays, pay

careful attention to capacitive loading. See the Output

Capacitive Loading and Stability section for more infor-

mation.

Table 1. Recommended Component Values

COMPONENT

GAIN (V/V)

+1

-1

+2

-2

+5

-5

+10

-10

+25

-25

RF (Ω)

24

500

500

500

500

500

500

500

500

1200

RG (Ω)

∞

500

500

250

124

100

56

50

20

50

RS (Ω)

—

0

—

0

—

0

—

0

—

0

RTIN (Ω)

49.9

56

49.9

62

49.9

100

49.9

∞

49.9

∞

RTO (Ω)

49.9

49.9

49.9

49.9

49.9

49.9

49.9

49.9

49.9

49.9

Small-Signal -3dB Bandwidth (MHz)

200

90

105

60

25

33

11

25

6

10

Note: RL = RO + RTO; RTIN and RTO are calculated for 50Ω applications. For 75Ω systems, RTO = 75Ω; calculate RTIN from the

following equation:

TIN

G

75

R

75

1

R

=

Ω

−

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Analog Devices │ 11

MAX4012/MAX4016/

MAX4018/MAX4020

Low-Cost, High-Speed, Single-Supply

Op Amps with Rail-to-Rail Outputs