LMP7701MF/NOPB National Semiconductor, LMP7701MF/NOPB Datasheet  Page 17
LMP7701MF/NOPB
Manufacturer Part Number
LMP7701MF/NOPB
Description
IC OP AMP PREC 12V RRIO SOT235
Manufacturer
National Semiconductor
Series
LMP®r
Datasheet
1.LMP7701MFNOPB.pdf
(24 pages)
Specifications of LMP7701MF/NOPB
Amplifier Type
General Purpose
Number Of Circuits
1
Output Type
RailtoRail
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
SOT235, SC74A, SOT25
Number Of Channels
1
Voltage Gain Db
130 dB
Common Mode Rejection Ratio (min)
88 dB
Input Voltage Range (max)
12 V
Input Voltage Range (min)
2.7 V
Input Offset Voltage
0.2 mV at 5 V
Output Current (typ)
42 mA
Operating Supply Voltage
3 V, 5 V, 9 V
Supply Current
1 mA at 5 V
Maximum Operating Temperature
+ 125 C
Mounting Style
SMD/SMT
Minimum Operating Temperature
 40 C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
3db Bandwidth

Lead Free Status / Rohs Status
Details
Other names
LMP7701MF
LMP7701MFTR
LMP7701MFTR
PRECISION CURRENT SOURCE
The LMP7701/LMP7702/LMP7704 can each be used as a
precision current source in many different applications. Figure
6 shows a typical precision current source. This circuit imple
ments a precision voltage controlled current source. Amplifier
A1 is a differential amplifier that uses the voltage drop across
R
nates the error current from the load side of the R
that would flow in the feedback resistor if it were connected
to the load side of the R
stable as long as the closed loop bandwidth of amplifier A2 is
greater then the closed loop bandwidth of amplifier A1. Note
that if A1 and A2 are the same type of amplifiers, then the
feedback around A1 will reduce its bandwidth compared to
A2.
The equation for output current can be derived as follows:
Solving for the current I results in the following equation:
LOW INPUT VOLTAGE NOISE
The LMP7701/LMP7702/LMP7704 have the very low input
voltage noise of 9 nV/
further reduced by placing N amplifiers in parallel as shown
in Figure 7. The total voltage noise on the output of this circuit
S
as the feedback signal. Amplifier A2 is a buffer that elimi
FIGURE 6. Precision Current Source
S
. This input voltage noise can be
resistor. In general, the circuit is
S
resistor
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is divided by the square root of the number of amplifiers used
in this parallel combination. This is because each individual
amplifier acts as an independent noise source, and the aver
age noise of independent sources is the quadrature sum of
the independent sources divided by the number of sources.
For N identical amplifiers, this means:
Figure 7 shows a schematic of this input voltage noise reduc
tion circuit. Typical resistor values are:
R
G
= 10Ω, R
FIGURE 7. Noise Reduction Circuit
F
= 1 kΩ, and R
O
= 1 kΩ.
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