MAX4029(2004) データシートの表示（PDF） - Maxim Integrated
部品番号
コンポーネント説明
メーカー
MAX4029 Datasheet PDF : 13 Pages
| |||
Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps
SMALL-SIGNAL BANDWIDTH
vs. FREQUENCY
11
10
CLOAD = 15pF
9
8
CLOAD = 10pF
7
6
5
4
CLOAD = 5pF
3
2
1
100k
1M
10M
100M
1G
FREQUENCY (Hz)
Figure 4. Small-Signal Gain vs. Frequency with Capacitive
Load and No Isolation Resistor
OPTIMAL ISOLATION RESISTANCE
vs. CAPACITIVE LOAD
30
25
20
15
10
5
0
0
50 100 150 200 250
CLOAD (pF)
Figure 6. Optimal Isolation Resistance vs. Capacitive Load
A/B
75Ω CABLE 0.1µF
IN_A
RT
75Ω
DISABLE
OUT_
RISO
75Ω CABLE 0.1µF
IN_B
RT
75Ω
CLAMP
CL
RL
RKEYREF
MAX4028
MAX4029
Figure 5. Using an Isolation Resistor (RISO) for a High-
Capacitive Load
Although the MAX4028/MAX4029 are optimized for AC
performance and are not designed to drive highly
capacitive loads, they are capable of driving up to
15pF without oscillations. However, some peaking may
occur in the frequency domain (Figure 4). To drive larg-
er capacitive loads or to reduce ringing, add an isola-
tion resistor between the amplifier’s output and the load
(Figure 5). The value of RISO depends on the circuit’s
gain (+2V/V) and the capacitive load (Figure 6). Also
note that the isolation resistor forms a divider that
decreases the voltage delivered to the load.
Layout and Power-Supply Bypassing
The MAX4028/MAX4029 have high bandwidths and
consequently require careful board layout, including
the possible use of constant-impedance microstrip or
stripline techniques.
To realize the full AC performance of these high-speed
amplifiers, pay careful attention to power-supply
bypassing and board layout. The PC board should
have at least two layers: a signal and power layer on
one side, and a large, low-impedance ground plane on
the other side. The ground plane should be as free of
voids as possible. Whether or not a constant-imped-
ance board is used, it is best to observe the following
guidelines when designing the board:
1) Do not use wire-wrapped boards or breadboards.
2) Do not use IC sockets; they increase parasitic
capacitance and inductance.
3) Keep signal lines as short and straight as possible.
Do not make 90° turns; round all corners.
4) Observe high-frequency bypassing techniques to
maintain the amplifier’s accuracy and stability.
5) Use surface-mount components. They generally
have shorter bodies and lower parasitic reactance,
yielding better high-frequency performance than
through-hole components.
10 ______________________________________________________________________________________
Share Link: 