where:

The MAX4104/MAX4105/MAX4304/MAX4305 have a

very low, 2.1nV/

√Hz input voltage noise density and

3.1pA/

√Hz input current noise density.

An example of DC-error calculations, using the

MAX4304 typical data and the typical operating circuit

gives:

Calculating total output noise in a similar manner yields

the following:

With a 200MHz system bandwidth, this calculates to

sigma calculation).

ADC Input Buffers

Input buffer amplifiers can be a source of significant

error in high-speed ADC applications. The input buffer

is usually required to rapidly charge and discharge the

ADC’s input, which is often capacitive. In addition, the

input impedance of a high-speed ADC often changes

very rapidly during the conversion cycle—a condition

that demands an amplifier with very low output imped-

ance at high frequencies to maintain measurement

accuracy. The combination of high-speed, fast slew

rate, low noise, and low-distortion available in the

MAX4104/MAX4105/MAX4304/MAX4305 makes them

ideally suited for use as buffer amplifiers in high-speed

ADC applications.

Video Line Driver

The MAX4104/MAX4105/MAX4304/MAX4305 are opti-

mized to drive coaxial transmission lines when the

cable is terminated at both ends, as shown in Figure 2.

To minimize reflections and maximize power transfer,

select the termination resistors to match the character-

istic impedance of the transmission line. Cable frequen-

cy response can cause variations in the flatness of the

signal.

Driving Capacitive Loads

The MAX4104/MAX4105/MAX4304/MAX4305 provide

maximum AC performance when driving no output load

capacitance. This is the case when driving a correctly

terminated transmission line (i.e., a back-terminated

cable).

In most amplifier circuits, driving a large load capaci-

tance increases the chance of oscillations occurring.

The amplifier’s output impedance and the load capaci-

tor combine to add a pole and excess phase to the

loop response. If the pole’s frequency is low enough

and phase margin is degraded sufficiently, oscillations

may result.

A second concern when driving capacitive loads origi-

nates from the amplifier’s output impedance, which

e

x

x

x

x

x

e

nV Hz

n OUT

n OUT

(

)

(

)

.

.

.

.

=

+



 +







 +









=

−

−

−

1 1

3 1

10

50

3 1

10

165

2 1

10

4 3

12

2

12

2

9

2

V

32 x 10

50

32 x 10

165

1 x 10

1

1

V

15.8mV

OUT

6

6

3

OUT

= 

















+

[

]

=

−

−

−

Ω

740MHz, Low-Noise, Low-Distortion

Op Amps in SOT23-5

10

______________________________________________________________________________________

MAX4104

MAX4105

MAX4304

MAX4305

FB

IN

OUT

Figure 1. Output Offset Voltage

Figure 2. Video Line Driver

MAX4104

MAX4105

MAX4304

MAX4305

IN-

IN+

OUT

75

Ω

75

Ω

75

Ω

75

Ω CABLE

75

Ω CABLE