4181 查看數據表（PDF） - Maxim Integrated
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4181 Datasheet PDF : 24 Pages
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Single/Dual/Quad, 270MHz, 1mA, SOT23,
Current-Feedback Amplifiers with Shutdown
The MAX4180–MAX4187 have a very low, 2nV/√Hz
noise voltage. The current noise at the positive input
(in+) is 4pA/√Hz, and the current noise at the inverting
input is 5pA/√Hz.
An example of the DC error calculations, using the
MAX4180 typical data and typical operating circuit
where RF = RG = 1.2kΩ (RF || RG = 600Ω) and
RS = 37.5Ω, gives the following:
( ) ( ) VOUT = 1x10−6 x37.5 + 2x10−6 x 255 + 1.5x10−3 x 1+ 1
VOUT = 4.1mV
Calculating the total output noise in a similar manner
yields:
( ) en(OUT) = 1+1
4x10−12 x37.5 2 + 5x10−12 x255 2
+ 2x10−9 2
en(OUT) = 4.8nV/ Hz
With a 200MHz system bandwidth, this calculates to
102µVRMS (approximately 612µVp-p, choosing the six-
sigma value).
Video Line Driver
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 RF and RG values.
Driving Capacitive Loads
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, RS,
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-
RG
IB-
IB+
RS
RF
VOUT
MAX4180–MAX4187
VIN
RS
RG
RT
RF
VOUT
RO
VOUT = -(RF / RG) x VIN
MAX4180–MAX4187
Figure 4a. Inverting Gain Configuration
VIN
RS
RG
RT
RF
VOUT
RO
Figure 5. Output Offset Voltage
RG
820Ω
0.1µF
RF
820Ω
+5V
75Ω CABLE
MAX4180
VIDEO
IN
75Ω 0.1µF
75Ω 75Ω CABLE
75Ω
VIDEO
OUT
MAX4180–MAX4187
-5V
VOUT = [1+ (RF / RG) VIN
Figure 4b. Noninverting Gain Configuration
VIDEO LINE DRIVER
Figure 6. Video Line Driver
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