Ultra-Low-Distortion, Single-Supply,
300MHz Op Amps with Enable
be maintained using an amplifier with very low output
impedance at high frequencies. The combination of
20
high speed, fast slew rate, low noise, and a low and
stable distortion over load makes the MAX4265–
15
MAX4270 ideally suited for use as buffer amplifiers in
MAX4268
high-speed ADC applications.
MAX4269
10
Low-Power Disable Mode
The MAX4265–MAX4270 feature an active-high enable
pin that can be used to save power and place the out-
MAX4270
5
0
puts in a high-impedance state. Drive EN_ with logic
levels or connect EN_ to V for normal operation. In
CC
the dual versions (MAX4268/MAX4269/MAX4270),
each individual op amp is enabled separately, allowing
the devices to be used in a multiplex configuration. The
supply current in low-power mode is reduced to 1.6mA
per device. Enable time is typically 100ns, and disable
time is typically 750µs.
0
20
40
60
(pF)
80
100
120
C
LOAD
Figure 2. MAX4268/MAX4269/MAX4270 Isolation Resistance
vs. Capacitive Load
5
4
3
5
C = 7.3pF
L
4
3
C = 5.1pF
L
2
1
2
C = 5.1pF
L
1
0
0
-1
-2
-3
-1
-2
-3
C = 7.3pF
L
C = 2.2pF
L
C = 2.2pF
L
-4
-5
-4
-5
0.1M
1M
10M
FREQUENCY (Hz)
100M
1G
0.1M
1M
10M
FREQUENCY (Hz)
100M
1G
Figure 3a. MAX4268 Small-Signal Gain vs. Frequency
Without Isolation Resistor
Figure 3b. MAX4269 Small-Signal Gain vs. Frequency
Without Isolation Resistor
5
4
4
3
3
2
C = 10pF
ISO
2
1
L
C = 15pF
L
R
= 12Ω
C = 10pF
L
ISO
1
0
R
= 15Ω
0
-1
-2
-3
-4
C = 10pF
L
ISO
-1
-2
-3
C = 10pF
L
R
= 18Ω
C = 7.3pF
L
-4
-5
-5
-6
0.1M
1M
10M
FREQUENCY (Hz)
100M
1G
0.1M
1M
10M
FREQUENCY (Hz)
100M
1G
Figure 3c. MAX4270 Small-Signal Gain vs. Frequency
Without Isolation Resistor
Figure 4a. MAX4268 Small-Signal Gain vs. Frequency
With Isolation Resistor
12 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
