To drive larger-capacitance loads or to reduce ringing,

add an isolation resistor between the amplifier’s output

and the load, as shown in Figure 4.

capacitive load. Figure 5 shows the optional isolation

capacitor values, the bandwidth is dominated by the

Power-Dissipation Considerations

The MAX4137/MAX4138 can drive up to four outputs

simultaneously. Quiescent power dissipation is typically

520mW and 650mW maximum, respectively, with all

channels enabled. The maximum package power dissi-

pation is rated at 1540mW.

In a typical application, four outputs drive a standard

video signal into a 150

Ω load. The amount of power

added to the quiescent dissipation is minimal and no

special precautions are necessary.

However, each output driving the maximum 65mA into

30

Ω will cause a power-dissipation increase of approxi-

mately 200mW. Therefore, you should not allow more

than three outputs to deliver that load simultaneously.

Similarly, one output shorted to ground will cause a

power-dissipation increase of 650mW. Only one output

can be shorted to ground without violating the package

power rating.

In conclusion, during normal operation in a matched-

load environment, the total power dissipation is well

within the package’s dissipation rating. The maximum

power dissipation is violated only if multiple channels

are driving the maximum current into minimum loads at

the same time.

1-Input/4-Output

Video Distribution Amplifiers

10

______________________________________________________________________________________

14

12

10

8

0.1M

1M

10M

100M

1G

0

6

4

2

FREQUENCY (Hz)

MAX4137

MAX4138

Figure 4. Capacitive-Load Driving Circuit

10

40

70

100

130

160

190

220

10

11

12

13

14

15

16