MAX4158 Datasheet, PDF (13/16 Pages) Maxim Integrated Products – 350MHz/250MHz, 2-Channel Video Multiplexer-Amplifiers

350MHz/250MHz, 2-Channel
Video Multiplexer-Amplifiers
R_G
R_F
FB
75Ω CABLE
INO
INI
R_T
75Ω
75Ω CABLE
R_T
75Ω
R_T
OUT _75Ω
75Ω CABLE
R_T
75Ω
MAX4158
MAX4159
MAX4258
MAX4259
Figure 3. Video Line Driver
R_G
R_F
FB
OUT
R_ISO
IN_
C_L
R_L
MAX4158
MAX4159
MAX4258
MAX4259
Figure 4. Using an Isolation Resistor (R_ISO) for High
Capacitive Loads
Driving Capacitive Loads
A correctly terminated transmission line is purely resis-
tive and presents no capacitive load to the amplifier.
Consequently, the MAX4158/MAX4159/MAX4258/
MAX4259 are optimized for AC performance and are
not designed to drive highly capacitive loads. Reactive
loads will decrease phase margin and may produce
excessive ringing and oscillation (see Typical
Operating Characteristics). The circuit of Figure 4
reduces this problem. The small (usually 5Ω to 20Ω)
isolation resistor R_ISO, placed before the reactive load,
prevents ringing and oscillation. At higher capacitive
loads, AC performance is limited by the interaction of
load capacitance with the isolation resistor.
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