Single/Dual/Quad, 270MHz, 1mA, SOT23,

Current-Feedback Amplifiers with Shutdown

18

______________________________________________________________________________________

The MAX4180–MAX4187 have a very low, 2nV/

√Hz

noise voltage. The current noise at the positive input

input is 5pA/

√Hz.

An example of the DC error calculations, using the

MAX4180 typical data and typical operating circuit

Calculating the total output noise in a similar manner

yields:

With a 200MHz system bandwidth, this calculates to

sigma value).

Video Line Driver

The MAX4180–MAX4187 are well suited to drive coaxi-

al transmission lines when the cable is terminated at

both ends, as shown in Figure 6. Cable frequency

response can cause variations in the signal’s flatness.

Driving Capacitive Loads

The MAX4180–MAX4187 are optimized for AC perfor-

mance. They are not designed to drive highly capaci-

tive loads. Reactive loads decrease phase margin and

may produce excessive ringing and oscillation. Figure

7a shows a circuit that eliminates this problem. Placing

the small (usually 5

before the reactive load prevents ringing and

oscillation. At higher capacitive loads, the interaction of

the load capacitance and isolation resistor controls AC

performance. Figures 7b and 7c show the MAX4180

and MAX4181 frequency response with a 47pF capaci-

e1 1

4x10

x37.5

5x10

x255

2x10

e

4.8nV/ Hz

n(OUT)

12

2

12

2

9

2

n(OUT)

=+

()









+ 







+ 







=

−−

−

V

1x10

x37.5

2x10

x 255

1.5x10

x 1 1

V

4.1mV

OUT

66

3

OUT

=+

+

+

=

−−

−





















VIDEO

IN

VIDEO

OUT

75

Ω

75

Ω CABLE

VIDEO LINE DRIVER

75

Ω CABLE

820

Ω

820

Ω

75

Ω

75

Ω

+5V

-5V

0.1µF

MAX4180

0.1µF

Figure 6. Video Line Driver

MAX4180–MAX4187

Figure 4a. Inverting Gain Configuration

MAX4180–MAX4187

Figure 4b. Noninverting Gain Configuration

MAX4180–MAX4187

Figure 5. Output Offset Voltage