
MAX4180–MAX4187
Single/Dual/Quad, 270MHz, 1mA, SOT23,
Current-Feedback Amplifiers with Shutdown
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17
Table 1. Recommended Component Values
245
1.2k
RL = 1k
190
680
RL =
100
-3dB BW (MHz)
190
820
RL = 150
RG (
)
RF (
)
COMPONENT/BW
76
56
560
RL =
1k
/150
AV = +10V/V
205
—
1k
RL =
150
120
270
—
2.4k
RL = 1k
130
520
RL =
1k
/150
AV = +5V/V
200
—
560
RL =
100
AV = +2V/V
AV = +1V/V
MAX4180
MAX4181
AV = +2V/V
245
1k
RL =
1k
160
MAX4182/MAX4183
620
RL =
100
-3dB BW
(MHz)
190
680
RL =
150
RG (
)
RF (
)
COMPONENT/
BW
AV = +2V/V
245
1.1k
RL =
1k
175
MAX4186
680
RL =
100
190
750
RL =
150
AV = +1V/V
270
—
1.6k
RL =
1k
200
MAX4187
—
680
RL =
100
205
—
910
RL =
150
AV = +1V/V
270
—
1.5k
RL =
1k
180
MAX4184/MAX4185
—
620
RL =
100
205
—
750
RL =
150
Choosing Feedback and Gain Resistors
The optimum value of the external-feedback (RF) and
gain-setting (RG) 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 (VOS) times the closed-loop
gain (1 = RF / RG).
The positive input bias current (IB+) times the source
resistor (RS) (usually 50
or 75), plus the negative
input bias current (IB-) times the parallel combination
of RG and RF. 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
iR
R
e
n OUT
F
G
nS
n
F
G
n
()
||
=+
()
+
()
+
()
+
1
22
2
VOUT
||
=
() + ()
() +
[] +
+
IR
I
R
V
R
BS
B
F
G
OS
F
G
1