MAX4105 Maxim, MAX4105 Datasheet - Page 11

• Manufacturer Part Number: MAX4105
• Description: The MAX4104/MAX4105/MAX4304/MAX4305 op amps feature ultra-high speed, low noise, and low distortion in a SOT23 package
• Manufacturer: Maxim

Figure 3c. MAX4105 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 R
capacitive load (Figure 5). Figure 6 shows the
MAX4104/MAX4105/MAX4304/MAX4305 frequency
response with the isolation resistor and a capacitive
Figure 3a. MAX4104 Frequency Response with Capacitive
Load and No Isolation Resistor
-10
-15
-20
-25
-10
-15
-20
25
20
15
10
30
25
20
15
10
-5
-5
5
0
5
0
100k
100k
ISO
depends on the circuit’s gain and the
______________________________________________________________________________________
1M
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
10M
10M
C
C
C
L
L
L
C
= 5pF
L
= 10pF
= 10pF
740MHz, Low-Noise, Low-Distortion
100M
100M
= 5pF
C
C
L
L
= 15pF
= 15pF
1G
1G
load. With higher capacitive values, bandwidth is domi-
nated by the RC network formed by R
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.
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
Figure 3b. MAX4304 Frequency Response with Capacitive
Load and No Isolation Resistor
Figure 3d. MAX4305 Frequency Response with Capacitive
Load and No Isolation Resistor
Maxim’s High-Speed Evaluation Boards
Op Amps in SOT23-5
-10
-15
-20
-25
-10
-15
-20
25
20
15
10
-5
30
25
20
15
10
-5
5
0
5
0
100k
100k
1M
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
10M
10M
C
L
C
C
L
= 10pF
L
C
100M
100M
= 5pF
= 10pF
L
= 5pF
C
C
L
L
= 15pF
= 15pF
1G
1G
ISO
and C
L
; the
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