MAX4018EEE datasheet(11/16 Pages) MAXIM

11 / 16 page

Maxim recommends using microstrip and stripline tech-

niques to obtain full bandwidth. To ensure that the PC

board does not degrade the amplifier’s performance,

design it for a frequency greater than 1GHz. Pay care-

ful attention to inputs and outputs to avoid large para-

sitic 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 possi-

ble. 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 nonlinear function of the input, but does not under-

go phase reversal or latchup.

The output swings to within 60mV of either power-

supply rail with a 2k

Ω 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 out-

put 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 nega-

tive supply rail, IIL increases (Figure 2). A single resis-

tor 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 35k

Ω. 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 information.

Low-Cost, High-Speed, SOT23, Single-Supply

Op Amps with Rail-to-Rail Outputs

______________________________________________________________________________________

RF (Ω)

500

RG (Ω)

∞

500

COMPONENT

RS (Ω)

—

RTIN (Ω)

49.9

Small-Signal -3dB Bandwidth (MHz)

200

RTO (Ω)

49.9

Table 1. Recommended Component Values

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

following equation:

500

—

49.9

105

49.9

500

250

49.9

500

124

—

49.9

500

100

49.9

500

—

49.9

500

∞

49.9

500

—

49.9

GAIN (V/V)

1200

∞

49.9

-1

-2

-5

+10

-10

+25

-25

TIN

Ω

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