following equation:

0.1µF capacitor as close to the pin as possible. If operat-

ing with dual supplies, bypass each supply with a 0.1µF

capacitor.

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 design guide-

lines:

• Don’t use wire-wrap boards; they are too inductive.

• Don’t use IC sockets; they increase parasitic capaci-

tance 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

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 55mV 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.

Output Capacitive Loading and Stability

The MAX4450/MAX4451 are optimized for AC perfor-

mance. They are not designed to drive highly reactive

loads, which decrease phase margin and may produce

excessive ringing and oscillation. Figure 2 shows a cir-

cuit that eliminates this problem. Figure 3 is a graph of

Figure 4 shows how a capacitive load causes exces-

sive peaking of the amplifier’s frequency response if

the capacitor is not isolated from the amplifier by a

resistor. A small isolation resistor (usually 20

Ω to 30Ω)

placed before the reactive load prevents ringing and

oscillation. At higher capacitive loads, AC performance

is controlled by the interaction of the load capacitance

and the isolation resistor. Figure 5 shows the effect of a

27

Ω isolation resistor on closed-loop response.

Coaxial cable and other transmission lines are easily

driven when properly terminated at both ends with their

characteristic impedance. Driving back-terminated

transmission lines essentially eliminates the line’s

capacitance.

Table 1. Recommended Component Values

Ultra-Small, Low-Cost, 210MHz, Single-Supply

Op Amps with Rail-to-Rail Outputs

8

_______________________________________________________________________________________

-25

+25

-10

+10

-5

+5

-2

+2

-1

+1

49.9

10

∞

0

50

1200

GAIN (V/V)

49.9

5

49.9

—

20

500

49.9

15

∞

0

50

500

49.9

11

49.9

—

56

500

49.9

25

100

0

100

500

49.9

25

49.9

—

124

500

49.9

50

62

0

250

500

49.9

95

49.9

—

500

500

49.9

49.9

Ω)

100

210

Small-Signal -3dB Bandwidth (MHz)

56

49.9

Ω)

0

—

Ω)

COMPONENT

500

∞

Ω)

500

24

Ω)

R

=

75

1-

75

R

TIN

G

Ω