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PDF LT1028 Data sheet ( Hoja de datos )
| Número de pieza | LT1028 | |
| Descripción | Ultralow Noise Precision High Speed Op Amps | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT1028 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
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FEATURES
n Voltage Noise
1.1nV/√Hz Max at 1kHz
0.85nV/√Hz Typ at 1kHz
1.0nV/√Hz Typ at 10Hz
35nVP-P Typ, 0.1Hz to 10Hz
n Voltage and Current Noise 100% Tested
n Gain-Bandwidth Product
LT1028: 50MHz Min
LT1128: 13MHz Min
n Slew Rate
LT1028: 11V/µs Min
LT1128: 5V/µs Min
n Offset Voltage: 40µV Max
n Drift with Temperature: 0.8µV/°C Max
n Voltage Gain: 7 Million Min
n Available in 8-Lead SO Package
APPLICATIONS
n Low Noise Frequency Synthesizers
n High Quality Audio
n Infrared Detectors
n Accelerometer and Gyro Amplifiers
n 350Ω Bridge Signal Conditioning
n Magnetic Search Coil Amplifiers
n Hydrophone Amplifiers
LT1028/LT1128
Ultralow Noise Precision
High Speed Op Amps
DESCRIPTION
The LT®1028(gain of –1 stable)/LT1128(gain of +1 stable)
achieve a new standard of excellence in noise performance
with 0.85nV/√Hz 1kHz noise, 1.0nV/√Hz 10Hz noise. This
ultralow noise is combined with excellent high speed
specifications (gain-bandwidth product is 75MHz for
LT1028, 20MHz for LT1128), distortion-free output, and
true precision parameters (0.1µV/°C drift, 10µV offset
voltage, 30 million voltage gain). Although the LT1028/
LT1128 input stage operates at nearly 1mA of collector
current to achieve low voltage noise, input bias current
is only 25nA.
The LT1028/LT1128’s voltage noise is less than the noise
of a 50Ω resistor. Therefore, even in very low source
impedance transducer or audio amplifier applications,
the LT1028/LT1128’s contribution to total system noise
will be negligible.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Ultralow Noise 1M TIA Photodiode Amplifier
VS+ 4.32k
0.1µF
PHOTO
DIODE
SFH213
VS–
D JFET
NXP
S BF862
4.99k
VS–
1M
0.5pF
–
LT1028
+
VS = ±15V
VOUT = ~0.4V + IPD • 1M
1028 TA01
Voltage Noise vs Frequency
10
MAXIMUM
VS = 15V
TA = 25°C
1/f CORNER = 14Hz
TYPICAL
1
1/f CORNER = 3.5Hz
0.1
0.1
1 10 100
FREQUENCY (Hz)
1k
1028 TA02
For more information www.linear.com/LT1028
1028fd
1
1 page  
LT1028/LT1128
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating
temperature range –40°C ≤ TA ≤ 85°C. VS = ±15V, unless otherwise noted. (Note 11)
LT1028AC
LT1128AC
LT1028C
LT1128C
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX MIN TYP MAX
VOS
∆VOS
∆Temp
Input Offset Voltage
Average Input Offset Drift
(Note 8)
l 20 95
35 150
l 0.2 0.8 0.25 1.0
IOS Input Offset Current
IB Input Bias Current
Input Voltage Range
VCM = 0V
VCM = 0V
l
l
l ±10.4
20 80
±35 ±140
±11.8
±10.4
28
±45
±11.8
160
±280
CMRR
PSRR
AVOL
VOUT
IS
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Large-Signal Voltage Gain
Maximum Output Voltage Swing
Supply Current
VCM = ±10.5V
VS = ±4.5V to ±18V
RRLL
≥
≥
2k,
1k,
VVOO
=
=
±10V
±10V
RL ≥ 2k
l 108
123
102 123
l 112
131
106 131
l 4.0
3.0
20.0
14.0
2.5 20.0
2.0 14.0
l ±11.0 ±12.5
±11.0 ±12.5
l 8.5 11.0 8.7 12.5
UNITS
µV
µV/°C
nA
nA
V
dB
dB
V/µV
V/µV
V
mA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: Input Offset Voltage measurements are performed by automatic
test equipment approximately 0.5 sec. after application of power. In
addition, at TA = 25°C, offset voltage is measured with the chip heated
to approximately 55°C to account for the chip temperature rise when the
device is fully warmed up.
Note 3: Long Term Input Offset Voltage Stability refers to the average
trend line of Offset Voltage vs Time over extended periods after the first 30
days of operation. Excluding the initial hour of operation, changes in VOS
during the first 30 days are typically 2.5µV.
Note 4: This parameter is tested on a sample basis only.
Note 5: 10Hz noise voltage density is sample tested on every lot with the
exception of the S8 and S16 packages. Devices 100% tested at 10Hz are
available on request.
Note 6: Current noise is defined and measured with balanced source
resistors. The resultant voltage noise (after subtracting the resistor noise
on an RMS basis) is divided by the sum of the two source resistors to
obtain current noise. Maximum 10Hz current noise can be inferred from
100% testing at 1kHz.
Note 7: Gain-bandwidth product is not tested. It is guaranteed by design
and by inference from the slew rate measurement.
Note 8: This parameter is not 100% tested.
Note 9: The inputs are protected by back-to-back diodes. Current-limiting
resistors are not used in order to achieve low noise. If differential input
voltage exceeds ±1.8V, the input current should be limited to 25mA.
Note 10: This parameter guaranteed by design, fully warmed up at TA
= 70°C. It includes chip temperature increase due to supply and load
currents.
Note 11: The LT1028/LT1128 are designed, characterized and expected to
meet these extended temperature limits, but are not tested at –40°C and
85°C. Guaranteed I-grade parts are available. Consult factory.
For more information www.linear.com/LT1028
1028fd
5
5 Page 
LT1028/LT1128
APPLICATIONS INFORMATION – NOISE
Voltage Noise vs Current Noise
The LT1028/LT1128’s less than 1nV/√Hz voltage noise is
three times better than the lowest voltage noise heretofore
available (on the LT1007/1037). A necessary condition for
such low voltage noise is operating the input transistors at
nearly 1mA of collector currents, because voltage noise is
inversely proportional to the square root of the collector
current. Current noise, however, is directly proportional
to the square root of the collector current. Consequently,
the LT1028/LT1128’s current noise is significantly higher
than on most monolithic op amps.
Therefore, to realize truly low noise performance it is
important to understand the interaction between voltage
noise (en), current noise (In) and resistor noise (rn).
Total Noise vs Source Resistance
The total input referred noise of an op amp is given by:
et = [en2 + rn2 + (InReq)2]1/2
where Req is the total equivalent source resistance at the
two inputs, and
rn = √4kTReq = 0.13√Req in nV/√Hz at 25°C
As a numerical example, consider the total noise at 1kHz
of the gain 1000 amplifier shown in Figure 1.
the largest term, as in the example above, and the LT1028/
LT1128’s voltage noise becomes negligible. As Req is
further increased, current noise becomes important. At
1kHz, when Req is in excess of 20k, the current noise
component is larger than the resistor noise. The total
noise versus matched source resistance plot illustrates
the above calculations.
The plot also shows that current noise is more dominant
at low frequencies, such as 10Hz. This is because resistor
noise is flat with frequency, while the 1/f corner of current
noise is typically at 250Hz. At 10Hz when Req > 1k, the
current noise term will exceed the resistor noise.
When the source resistance is unmatched, the total noise
versus unmatched source resistance plot should be con-
sulted. Note that total noise is lower at source resistances
below 1k because the resistor noise contribution is less.
When RS > 1k total noise is not improved, however. This
is because bias current cancellation is used to reduce
input bias current. The cancellation circuitry injects two
correlated current noise components into the two inputs.
With matched source resistors the injected current noise
creates a common-mode voltage noise and gets rejected
by the amplifier. With source resistance in one input only,
the cancellation noise is added to the amplifier’s inherent
noise.
100Ω
100k
100Ω
–
LT1028
LT1128
+
In summary, the LT1028/LT1128 are the optimum am-
plifiers for noise performance, provided that the source
resistance is kept low. The following table depicts which op
amp manufactured by Linear Technology should be used
to minimize noise, as the source resistance is increased
beyond the LT1028/LT1128’s level of usefulness.
Figure 1
1028 F01
Req = 100Ω + 100Ω || 100k ≈ 200Ω
rn = 0.13√200 = 1.84nV√Hz
en = 0.85nV√Hz
In = 1.0pA/√Hz
et = [0.852 + 1.842 + (1.0 × 0.2)2]1/2 = 2.04nV/√Hz
Output noise = 1000 et = 2.04µV/√Hz
At very low source resistance (Req < 40Ω) voltage noise
dominates. As Req is increased resistor noise becomes
Table 1. Best Op Amp for Lowest Total Noise vs Source Resistance
SOURCE RESIS-
BEST OP AMP
TANCE (Ω) (Note 1) AT LOW FREQ (10Hz) WIDEBAND (1kHz)
0 to 400
LT1028/LT1128
LT1028/LT1128
400 to 4k
LT1007/1037
LT1028/LT1128
4k to 40k
LT1001
LT1007/LT1037
40k to 500k
LT1012
LT1001
500k to 5M
LT1012 or LT1055
LT1012
>5M LT1055 LT1055
Note 1: Source resistance is defined as matched or unmatched, e.g.,
RS = 1k means: 1k at each input, or 1k at one input and zero at the other.
For more information www.linear.com/LT1028
1028fd
11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LT1028.PDF ] | |
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