Low-Cost, +3V/+5V, 620µA, 200MHz,

Single-Supply Op Amps with Rail-to-Rail Outputs

12

______________________________________________________________________________________

Active Filters

The low distortion and high bandwidth of the

MAX4452/MAX4453/MAX4454

and

MAX4352/

MAX4353/MAX4354 make them ideal for use in active

filter circuits. Figure 4 is a 15MHz lowpass multiple

feedback active filter using the MAX4452.

ADC Input Buffer

Input buffer amplifiers can be a source of significant

errors in high-speed ADC applications. The input buffer

is usually required to rapidly charge and discharge the

ADC’s input, which is often capacitive. See Output

Capacitive Loading and Stability. In addition, since a

high-speed ADC’s input impedance often changes very

rapidly during the conversion cycle, measurement

accuracy must be maintained using an amplifier with

very low output impedance at high frequencies. The

combination of high speed, fast slew rate, low noise,

and a low and stable distortion over load makes the

MAX4452/MAX4453/MAX4454/MAX4352/MAX4353/

MAX4354 ideally suited for use as buffer amplifiers in

high-speed ADC applications.

Layout and Power-Supply Bypassing

These amplifiers operate from a single +2.7V to +5.25V

capacitor as close to the pin as possible.

Maxim recommends using microstrip and stripline tech-

niques to obtain full bandwidth. Design the PC board

for a frequency greater than 1GHz to prevent amplifier

performance degradation due to board parasitics.

Avoid large parasitic capacitance at inputs and out-

puts. Whether or not a constant-impedance board is

used, observe the following guidelines:

• Do not use wirewrap boards due to their high induc-

tance.

• Do not use IC sockets because of the increased

parasitic capacitance and inductance.

Gain

R2

R1

0

1

2p

1

R2

R3

C1 C2

C2

C1 C2 R2 R3

1

R1

1

R2

1

R3

=

ƒ =

××

×

=

××

×

++

-

Q

IN

Figure 3b. Inverting Gain Configuration

IN

Figure 3a. Noninverting Gain Configuration

C1

100pF

R2

150

Ω

C2

15pF

R3

R1

511

Ω

150

Ω

10k

Ω

10k

Ω

+5.0V

Figure 4. Multiple-Feedback Lowpass Filter