Single/Dual/Quad, 400MHz, Low-Power,

Current Feedback Amplifiers

10

______________________________________________________________________________________

bandwidth is essentially independent of closed-loop

Layout and Power-Supply Bypassing

The MAX4112/MAX4113/MAX4117–MAX4120 have an

RF bandwidth and consequently require careful board

layout, including the possible use of constant-impedance

microstrip or stripline techniques.

To realize the full AC performance of these high-speed

amplifiers, pay careful attention to power-supply

bypassing and board layout. The PC board should

have at least two layers: a signal and power layer on

one side, and a large, low-impedance ground plane on

the other side. The ground plane should be as free of

voids as possible. With multilayer boards, locate the

ground plane on a layer that incorporates no signal or

power traces.

Regardless of whether a constant-impedance board is

used, observe the following guidelines when designing

the board. Wire-wrapped boards are much too induc-

tive, and breadboards are much too capacitive; neither

should be used. IC sockets increase parasitic capaci-

tance and inductance, and should not be used. In gen-

eral, surface-mount components give better high-

frequency performance than through-hole components.

They have shorter leads and lower parasitic reac-

tances. Keep lines as short and as straight as possible.

Do not make 90° turns; round all corners.

Observe high-frequency bypassing techniques to

maintain the amplifier’s accuracy. The bypass capaci-

tors should include a 1000pF ceramic capacitor

between each supply pin and the ground plane, locat-

ed as close to the package as possible. Next, place a

0.01µF to 0.1µF ceramic capacitor in parallel with each

1000pF capacitor, and as close to them as possible.

Then place a 10µF to 15µF low-ESR tantalum at the

point of entry (to the PC board) of the power-supply

pins. The power-supply trace should lead directly from

minimize parasitic inductance, keep PC traces short

and use surface-mount components.

V

V

G

1

R / R

OUT

IN

F

G

=

=

+

(

)

MAX4112

MAX4113

MAX4117

MAX4118

MAX4119

MAX4120

Figure 2a. Inverting Gain Configuration

MAX4112

MAX4113

MAX4117

MAX4118

MAX4119

MAX4120

Figure 2b. Noninverting Gain Configuration

100

49.9

400

49.9

600

600

100

0.1dB Gain Flatness (MHz)

49.9

400

-3dB Small-Signal Bandwidth (MHz)

100

49.9

270

49.9

500

500

49.9

600

115

600

49.9

300

49.9

47

330

115

49.9

270

115

49.9

300

49.9

47

330

49.9

69

500

MAX4117

MAX4119

MAX4112

MAX4118

MAX4120

MAX4113

Table 1. Recommended Component Values

280

280

Large-Signal Bandwidth (MHz)

145

240

240

240

COMPONENT