MAX4181 Maxim, MAX4181 Datasheet - Page 18

• Manufacturer Part Number: MAX4181
• Description: The MAX4180 family of current-feedback amplifiers combines high-speed performance, low distortion,and excellent video specifications with ultra-low-power operation in miniature packages
• Manufacturer: Maxim

Single/Dual/Quad, 270MHz, 1mA, SOT23,
Current-Feedback Amplifiers with Shutdown
Figure 4a. Inverting Gain Configuration
Figure 4b. Noninverting Gain Configuration
18
The MAX4180–MAX4187 have a very low, 2nV/√Hz
noise voltage. The current noise at the positive input
(i
input is 5pA/√Hz.
An example of the DC error calculations, using the
MAX4180 typical data and typical operating circuit
where R
R
Calculating the total output noise in a similar manner
yields:
With a 200MHz system bandwidth, this calculates to
102µV
sigma value).
V
V
n+
S
V
OUT
OUT
IN
V
e
e
OUT
V
= 37.5Ω, gives the following:
) is 4pA/√Hz, and the current noise at the inverting
V
n(OUT)
n(OUT)
IN
OUT
______________________________________________________________________________________
= -(R
=
=
RMS
= [1+ (R
4.1mV

 


R
F
1x10
S
F
R
/ R
= +
=
R
T
S
(approximately 612µVp-p, choosing the six-
R
G
( )
= R
F
1 1
4.8nV/ Hz
) x V
T
/ R
−
6
G
IN


) V
G
x37.5
R
IN


+  
G
4 x 10
R
= 1.2kΩ (R
G
2 x 10
+
−


12
2x10
−
9
x 37.5


2
−
R
6
F


R
F
x 600

 +
F
( )
2
|| R
MAX4180–MAX4187


MAX4180–MAX4187
5 x 10
G
+
1.5x10
= 600Ω) and
R
O
−
R
12
O
x 255
−
3
V
OUT

 
V
x 1 1
OUT
( )


2
+
The MAX4180–MAX4187 are well suited to drive coaxi-
al transmission lines when the cable is terminated at
both ends, as shown in Figure 6. Cable-frequency
response can cause variations in the signal’s flatness.
See Table 1 for optimum R
The MAX4180–MAX4187 are optimized for AC perfor-
mance. They are not designed to drive highly capaci-
tive loads. Reactive loads decrease phase margin and
may produce excessive ringing and oscillation. Figure
7a shows a circuit that eliminates this problem. Placing
the small (usually 5Ω to 22Ω) isolation resistor, R
before the reactive load prevents ringing and
oscillation. At higher capacitive loads, the interaction of
the load capacitance and isolation resistor controls AC
performance. Figures 7b and 7c show the MAX4180
and MAX4181 frequency response with a 47pF capaci-
Figure 6. Video Line Driver
Figure 5. Output Offset Voltage
VIDEO
IN
75Ω CABLE
820Ω
75Ω
R
G
0.1µF
0.1µF
R
R
G
S
MAX4180
VIDEO LINE DRIVER
I
I
B
B
820Ω
-
-5V
+
+5V
R
Driving Capacitive Loads
F
F
and R
0.1µF
R
F
MAX4180–MAX4187
Video Line Driver
75Ω
G
values.
75Ω CABLE
V
OUT
75Ω
VIDEO
OUT
S
,