MAX4118ESA+ Maxim Integrated, MAX4118ESA+ Datasheet - Page 11

• Manufacturer Part Number: MAX4118ESA+
• Description: High Speed Operational Amplifiers
• Manufacturer: Maxim Integrated

Specifications of MAX4118ESA+

• Rohs: yes
• Number Of Channels: 2
• Input Offset Voltage: 8 mV
• Slew Rate: 1800 V/us
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8 Narrow
• Common Mode Rejection Ratio (min): 45 dB
• Maximum Power Dissipation: 471 mW
• Minimum Operating Temperature: - 40 C

Figure 3. Output Offset Voltage
The MAX4112/MAX4113/MAX4117–MAX4120 are cur-
rent feedback amplifiers. Increasing feedback resistor
values will decrease peaking. Use the input resistor
(R
shows the standard inverting and noninverting configu-
rations. Notice that the gain of the noninverting circuit
(Figure 2b) is 1 plus the magnitude of the inverting
closed-loop gain (Table 1).
There are several major error sources to consider in
any operational amplifier. These apply equally to the
MAX4112/MAX4113/MAX4117–MAX4120. Offset-error
terms are given by the equation below. Voltage and
current-noise errors are root-square summed and
therefore computed separately. In Figure 3, the total
output offset voltage is determined by:
a) The input offset voltage (V
b) The positive input bias current (I
c) The total output-referred noise voltage is:
The MAX4112/MAX4117/MAX4119 have a very low,
2nV/√Hz noise voltage. The current noise at the positive
input (i
inverting input (i
e
n OUT
G
gain (1 + (R
resistor (R
input bias current (I
of R
the input bias currents may flow into or out of the
device. For this reason, there is no benefit to match-
ing the resistance at both inputs.
(
The equation for total DC error is:
) to change the magnitude of the gain. Figure 2
V
Choosing Feedback and Gain Resistors
OUT
MAX4112
MAX4113
MAX4117
MAX4118
MAX4119
MAX4120
G
)
n+
=
and R
) is 13pA/√Hz, and the current noise at the
⎛
⎜
⎝
=
1
+
S
[
( )
) (usually 50Ω or 75Ω), plus the negative
I
R
F
B
R
F
n-
+
G
F
/ R
. In current-mode feedback amplifiers,
) is 14pA/√Hz.
R
⎞
⎟
⎠
______________________________________________________________________________________
G
S
[
)).
+
( )
Single/Dual/Quad, 400MHz, Low-Power,
i
n
B-
( )
I
+
B
R
R
) times the parallel combination
G
S
−
R
(
S
R
I
I
]
B
B
F
2
-
+
OS
DC and Noise Errors
||
+
R
) times the closed-loop
[
( )
G
i
n
B+
)
−
+
R
R
) times the source
F
V
F
OS
||
]
R
⎛
⎜
⎝
G
1+
]
2
Current Feedback Amplifiers
R
R
+
G
F
V
( )
OUT
e
⎞
⎟
⎠
n
2
An example of the DC error calculations, using the
MAX4112 typical data and the typical operating circuit
where R
gives the following:
V
V
Calculating total output noise in a similar manner yields:
With a 200MHz system bandwidth, this calculates to
133µV
sigma value).
Surface-mount resistors are the best choice for high-
frequency circuits. They are of similar material to metal-
film resistors, but are deposited using a thick-film
process in a flat, linear manner that minimizes induc-
tance. Their small size and lack of leads also minimizes
parasitic inductance and capacitance, yielding more
predictable performance.
Metal-film resistors with leads are manufactured using
a thin-film process where resistive material is deposited
in a spiral layer around a ceramic rod. Although the
materials used are noninductive, the spiral winding pre-
sents a small inductance (about 5nH) that may have an
adverse effect on high-frequency circuits.
Carbon-composition resistors with leads are manufac-
tured by pouring the resistor material into a mold. This
process yields relatively low-inductance resistors that
are very useful in high-frequency applications, although
they tend to cost more and have more thermal noise
than other types. The ability of carbon-composition
resistors to self-heal after a large current overload
makes them useful in high-power RF applications.
For general-purpose use, surface-mount metal-film
resistors seem to have the best overall performance for
low cost, low inductance, and low noise.
The MAX4112/MAX4113/MAX4117–MAX4120 are opti-
mized (gain flatness) to drive coaxial transmission lines
when the cable is terminated at both ends, as shown in
Figure 4. Cable frequency response can cause varia-
tions in the flatness of the signal.
e
e
OUT
OUT
n(OUT)
n(OUT)
= (3.5 x 10
= 4.45mV
RMS
=
=
F
( )
1 1
= R
9.4nV Hz
+
(approximately 797µV
G
(
/
13x10
= 600Ω (R
-6
x 50 + 3.5 x 10
−
12
x50
F
)
2
||
+
R
(
14x10
G
= 300Ω) and R
-6
Video Line Driver
P-P
x 300 + 10
−
Resistor Types
12
, choosing the six-
x300
)
2
+
-3
(
2x10
S
) (1 + 1)
= 50Ω,
−
9
)
11
2