LMP7701MAX/NOPB National Semiconductor, LMP7701MAX/NOPB Datasheet - Page 16

• Manufacturer Part Number: LMP7701MAX/NOPB
• Description: IC OP AMP PREC RRIO SGL 8-SOIC
• Manufacturer: National Semiconductor
• Series: LMP®r

Specifications of LMP7701MAX/NOPB

• Amplifier Type: General Purpose
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 1.1 V/µs
• Gain Bandwidth Product: 2.5MHz
• Current - Input Bias: 0.2pA
• Voltage - Input Offset: 37µV
• Current - Supply: 790µA
• Current - Output / Channel: 86mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 12 V, ±1.35 V ~ 6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Other names: LMP7701MAX

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This equation is rearranged to find the location of the two
poles:
As shown in Equation 1, as values of R
the magnitude of the poles is reduced, which in turn decreas-
es the bandwidth of the amplifier. Whenever possible, it is
best to choose smaller feedback resistors. Figure 3 shows the
effect of the feedback resistor on the bandwidth of the
LMP7701/LMP7702/LMP7704.
Equation 1 has two poles. In most cases, it is the presence of
pairs of poles that causes gain peaking. In order to eliminate
this effect, the poles should be placed in Butterworth position,
since poles in Butterworth position do not cause gain peaking.
To achieve a Butterworth pair, the quantity under the square
root in Equation 1 should be set to equal −1. Using this fact
and the relation between R
value for R
is chosen to be larger than this optimum value, gain peaking
will occur.
In Figure 2, C
and to increase stability. Additionally, C
FIGURE 3. Closed Loop Gain vs. Frequency
1
can be found. This is shown in Equation 2. If R
F
is added to compensate for input capacitance
1
and R
2
, R
2
1
= −A
and R
F
V
reduces or elimi-
R
2
1
are increased,
, the optimum
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(1)
(2)
1
16
nates the gain peaking that can be caused by having a larger
feedback resistor. Figure 4 shows how C
ing.
DIODES BETWEEN THE INPUTS
The LMP7701/LMP7702/LMP7704 have a set of anti-parallel
diodes between the input pins, as shown in Figure 5. These
diodes are present to protect the input stage of the amplifier.
At the same time, they limit the amount of differential input
voltage that is allowed on the input pins. A differential signal
larger than one diode voltage drop might damage the diodes.
The differential signal between the inputs needs to be limited
to ±300 mV or the input current needs to be limited to ±10 mA.
FIGURE 4. Closed Loop Gain vs. Frequency with
FIGURE 5. Input of LMP7701
Compensation
F
reduces gain peak-
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