MAX4305 データシートの表示（PDF） - Maxim Integrated
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MAX4305 Datasheet PDF : 12 Pages
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740MHz, Low-Noise, Low-Distortion
Op Amps in SOT23-5
30
25
20
15
10
5
0
-5
-10
-15
-20
100k
CL = 15pF
CL = 10pF
CL = 5pF
1M 10M 100M 1G
FREQUENCY (Hz)
Figure 3a. MAX4104 Frequency Response with Capacitive
Load and No Isolation Resistor
30
25
20
15
10
5
0
-5
-10
-15
-20
100k
CL = 15pF
CL = 10pF
CL = 5pF
1M 10M 100M 1G
FREQUENCY (Hz)
Figure 3b. MAX4304 Frequency Response with Capacitive
Load and No Isolation Resistor
25
20
15
10
5
0
-5
-10
-15
-20
-25
100k
CL = 15pF
CL = 10pF
CL = 5pF
1M 10M 100M 1G
FREQUENCY (Hz)
25
20
15
10
5
0
-5
-10
-15
-20
-25
100k
CL = 15pF
CL = 10pF
CL = 5pF
1M 10M 100M 1G
FREQUENCY (Hz)
Figure 3c. MAX4105 Frequency Response with Capacitive
Load and No Isolation Resistor
Figure 3d. MAX4305 Frequency Response with Capacitive
Load and No Isolation Resistor
appears inductive at high frequencies. This inductance
forms an L-C resonant circuit with the capacitive load,
which causes peaking in the frequency response and
degrades the amplifier’s phase margin.
The MAX4104/MAX4105/MAX4304/MAX4305 drive
capacitive loads up to 10pF without oscillation.
However, some peaking may occur in the frequency
domain (Figure 3). To drive larger capacitance loads or
to reduce ringing, add an isolation resistor between the
amplifier’s output and the load (Figure 4).
The value of RISO depends on the circuit’s gain and the
capacitive load (Figure 5). Figure 6 shows the
MAX4104/MAX4105/MAX4304/MAX4305 frequency
response with the isolation resistor and a capacitive
load. With higher capacitive values, bandwidth is domi-
nated by the RC network formed by RISO and CL; the
bandwidth of the amplifier itself is much higher. Also
note that the isolation resistor forms a divider that
decreases the voltage delivered to the load.
Maxim’s High-Speed Evaluation Boards
The MAX4104 evaluation kit manual shows a suggest-
ed layout for Maxim’s high-speed, single-amplifier eval-
uation boards. This board was developed using the
techniques described previously (see Layout and
Power-Supply Bypassing section). The smallest avail-
able surface-mount resistors were used for the feed-
back and back-termination resistors to minimize the
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