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MAX4187EEE+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24
MAX4180–MAX4187
Single/Dual/Quad, 270MHz, 1mA, SOT23,
Current-Feedback Amplifiers with Shutdown
16 ______________________________________________________________________________________
• Keep lines as short and as straight as possible.
• Do not make 90° turns; round all corners.
• Observe high-frequency bypassing techniques to
maintain the amplifiers’ accuracy. The bypass cap-
acitors should include a 0.01µF to 0.1µF ceramic
capacitor between each supply pin and the ground
plane, located as close to the package as possible.
• Place a 1µF ceramic capacitor in parallel with each
0.01µF to 0.1µF capacitor as close to them as
possible.
• Place a 10µF to 15µF low-ESR tantalum at the point
of entry to the power-supply pins’ PC board. The
power-supply trace should lead directly from the
tantalum capacitor to the V
CC
and V
EE
pins.
• Keep PC traces short and use surface-mount com-
ponents to minimize parasitic inductance.
Maxim’s High-Speed Evaluation Board
Figures 2 and 3 show layouts of Maxim’s high-speed
single SOT23 and SO evaluation boards. These boards
were developed using the techniques described above.
The smallest available surface-mount resistors were
used for feedback and back-termination to minimize
their distance from the part, reducing the capacitance
associated with longer lead lengths.
SMA connectors were used for best high-frequency
performance. Because distances are extremely short,
performance is unaffected by the fact that inputs and
outputs do not match a 50Ω line. However, in applica-
tions that require lead lengths greater than one-quarter
of the wavelength of the highest frequency of interest,
use constant-impedance traces.
Fully assembled evaluation boards are available for the
MAX4180ESA.
Figure 2a. SOT23 High-Speed EV Board
Component Placement Guide—
Component Side
Figure 2b. SOT23 High-Speed EV Board
Layout—Component Side
Figure 2c. High-Speed EV Board Layout—
Solder Side
Figure 3a. SO-8 High-Speed EV Board
Component Placement Guide—
Component Side
Figure 3b. SO-8 High-Speed EV Board
Layout—Component Side
Figure 3c. SO-8 High-Speed EV Board
Layout—Solder Side
MAX4180–MAX4187
Single/Dual/Quad, 270MHz, 1mA, SOT23,
Current-Feedback Amplifiers with Shutdown
______________________________________________________________________________________ 17
Table 1. Recommended Component Values
245
1.2k
1.2k
R
L
= 1kΩ
190
680
680
R
L
=
100Ω
-3dB BW (MHz) 190
820
820
R
L
= 150Ω
R
G
(Ω)
R
F
(Ω)
COMPONENT/BW
76
56
560
R
L
=
1kΩ/150Ω
A
V
= +10V/V
205
—
1k
R
L
=
150Ω
120 270
—
2.4k
R
L
= 1kΩ
130
520
R
L
=
1kΩ/150Ω
A
V
= +5V/V
200
—
560
R
L
=
100Ω
A
V
= +2V/V A
V
= +1V/V
MAX4180 MAX4181
A
V
= +2V/V
245
1k
1k
R
L
=
1kΩ
160
MAX4182/MAX4183
620
620
R
L
=
100Ω
-3dB BW
(MHz)
190
680
680
R
L
=
150Ω
R
G
(Ω)
R
F
(Ω)
COMPONENT/
BW
A
V
= +2V/V
245
1.1k
1.1k
R
L
=
1kΩ
175
MAX4186
680
680
R
L
=
100Ω
190
750
750
R
L
=
150Ω
A
V
= +1V/V
270
—
1.6k
R
L
=
1kΩ
200
MAX4187
—
680
R
L
=
100Ω
205
—
910
R
L
=
150Ω
A
V
= +1V/V
270
—
1.5k
R
L
=
1kΩ
180
MAX4184/MAX4185
—
620
R
L
=
100Ω
205
—
750
R
L
=
150Ω
Choosing Feedback and Gain Resistors
The optimum value of the external-feedback (R
F
) and
gain-setting (R
G
) resistors used with the MAX4180–
MAX4187 depends on the closed-loop gain and the
application circuit’s load. Table 1 lists the optimum
resistor values for some specific gain configurations.
One-percent resistor values are preferred to maintain
consistency over a wide range of production lots.
Figures 4a and 4b show the standard inverting and
noninverting configurations. Note: The noninverting cir-
cuit gain (Figure 4) is 1 plus the magnitude of the
inverting closed-loop gain. Otherwise, the two circuits
are identical.
DC and Noise Errors
Several major error sources must be considered in any
op amp. These apply equally to the MAX4180–
MAX4187. Offset-error terms are given by the equation
below. Voltage and current-noise errors are root-square
summed and are therefore computed separately. In
Figure 5, the total output offset voltage is determined by
the following factors:
• The input offset voltage (V
OS
) times the closed-loop
gain (1 = R
F
/ R
G
).
• The positive input bias current (I
B+
) times the source
resistor (R
S
) (usually 50Ω or 75Ω), plus the negative
input bias current (I
B-
) times the parallel combination
of R
G
and R
F
. In current-feedback amplifiers, the
input bias currents at the IN+ and IN- terminals do
not track each other and may have opposite polarity,
so there is no benefit to matching the resistance at
both inputs.
The equation for the total DC error at the output is:
The total output-referred noise voltage is:
e
R
R
iR iRR e
n OUT
F
G
nS nFG n()
|| =+
()
+
()
+
()
+−
1
22
2
V
OUT
|| =
()
+
()
()
+
[]
+
+−
IR I R R V
R
R
BS B F G OS
F
G
1
MAX4180–MAX4187
Single/Dual/Quad, 270MHz, 1mA, SOT23,
Current-Feedback Amplifiers with Shutdown
18 ______________________________________________________________________________________
The MAX4180–MAX4187 have a very low, 2nV/√Hz
noise voltage. The current noise at the positive input
(i
n+
) 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 R
F
= R
G
= 1.2kΩ (R
F
|| R
G
= 600Ω) and
R
S
= 37.5Ω, gives the following:
Calculating the total output noise in a similar manner
yields:
With a 200MHz system bandwidth, this calculates to
102µV
RMS
(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 R
F
and R
G
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, R
S
,
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-
e11
4 x 10 x 37.5 5 x 10 x 255
2x10
e 4.8nV/ Hz
n(OUT)
12
2
12
2
9
2
n(OUT)
=+
()
+
+
=
−−
−
V 1x10 x37.5 2x10 x 600 1.5x10 x 1 1
V 4.1mV
OUT
OUT
66 3
=+++
=
−−
()
()
−
VIDEO
IN
VIDEO
OUT
75Ω
75Ω CABLE
VIDEO LINE DRIVER
75Ω CABLE
R
F
820Ω
R
G
820Ω
75Ω
75Ω
+5V
-5V
MAX4180
0.1µF
0.1µF
0.1µF
Figure 6. Video Line Driver
V
OUT
R
G
R
S
V
OUT
= -(R
F
/ R
G
) x V
IN
V
IN
R
F
R
O
R
T
MAX4180–MAX4187
Figure 4a. Inverting Gain Configuration
V
OUT
R
G
R
S
V
OUT
= [1+ (R
F
/ R
G
) V
IN
V
IN
R
F
R
O
R
T
MAX4180–MAX4187
Figure 4b. Noninverting Gain Configuration
R
G
I
B
-
I
B
+
V
OUT
R
F
R
S
MAX4180–MAX4187
Figure 5. Output Offset Voltage
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MAX4187EEE+T

Mfr. #:
Buy MAX4187EEE+T
Manufacturer:
Maxim Integrated
Description:
IC OPAMP CFA 245MHZ 16QSOP
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