MAX4220 Maxim, MAX4220 Datasheet - Page 12

• Manufacturer Part Number: MAX4220
• Description: The MAX4212/MAX4213 single, MAX4216 dual, MAX4218 triple, and MAX4220 quad op amps are unity-gain-stable devices that combine high-speed performance with Rail-to-Rail outputs
• Manufacturer: Maxim

Miniature, 300MHz, Single-Supply,
Rail-to-Rail Op Amps with Enable
Figure 2. Enable Logic-Low Input Current vs. V
Figure 4. Enable Logic-Low Input Current vs. V
Series Resistor
12
______________________________________________________________________________________
-100
-120
-140
-160
-20
-40
-60
-80
-10
20
-1
-2
-3
-4
-5
-6
-7
-8
-9
0
0
0
0
50 100 150
50 100 150
mV ABOVE V
mV ABOVE V
200 250
200 250
300 350
300 350
EE
EE
400 450
400 450
IL
IL
with 10k
500
500
The MAX4212/MAX4213/MAX4216/MAX4218/MAX4220
are optimized for AC performance. They are not
designed to drive highly reactive loads, which de-
creases phase margin and may produce excessive
ringing and oscillation. Figure 5 shows a circuit that
eliminates this problem. Figure 6 is a graph of the opti-
mal isolation resistor (R
shows how a capacitive load causes excessive peak-
ing of the amplifier’s frequency response if the capaci-
tor is not isolated from the amplifier by a resistor. A
small isolation resistor (usually 20
before the reactive load prevents ringing and oscilla-
tion. At higher capacitive loads, AC performance is
controlled by the interaction of the load capacitance
and the isolation resistor. Figure 8 shows the effect of a
27 isolation resistor on closed-loop response.
Coaxial cable and other transmission lines are easily
driven when properly terminated at both ends with their
characteristic impedance. Driving back-terminated
transmission lines essentially eliminates the line’s
capacitance.
Figure 3. Circuit to Reduce Enable Logic-Low Input Current
Output Capacitive Loading and Stability
IN-
IN+
MAX42_ _
ENABLE
S
) vs. capacitive load. Figure 7
EN_
10k
OUT
to 30 ) placed