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參數資料
| 型號： | AD797BRZ-REEL |
| 廠商： | Analog Devices Inc |
| 文件頁數： | 4/20頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC OPAMP GP 110MHZ ULDIST 8SOIC |
| 標準包裝： | 2,500 |
| 放大器類型： | 通用 |
| 電路數： | 1 |
| 轉換速率： | 20 V/µs |
| 增益帶寬積： | 110MHz |
| -3db帶寬： | 8MHz |
| 電流 - 輸入偏壓： | 250nA |
| 電壓 - 輸入偏移： | 10µV |
| 電流 - 電源： | 8.2mA |
| 電流 - 輸出 / 通道： | 50mA |
| 電壓 - 電源，單路/雙路(±)： | ±5 V ~ 15 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 8-SOIC（0.154"，3.90mm 寬） |
| 供應商設備封裝： | 8-SO |
| 包裝： | 帶卷 (TR) |
AD797
Data Sheet
Rev. J | Page 12 of 20
NOISE AND SOURCE IMPEDANCE CONSIDERATIONS
The AD797 ultralow voltage noise of 0.9 nV/√Hz is achieved
with special input transistors running at nearly 1 mA of collector
current. Therefore, it is important to consider the total input-
referred noise (eNtotal), which includes contributions from voltage
noise (eN), current noise (iN), and resistor noise (√4 kTRS).
2
/
1
2
]
)
(
4
[
S
N
S
N
R
i
kTR
e
total
e
×
+
=
(1)
where RS is the total input source resistance.
This equation is plotted for the AD797 in Figure 34. Because
optimum dc performance is obtained with matched source
resistances, this case is considered even though it is clear from
Equation 1 that eliminating the balancing source resistance
lowers the total noise by reducing the total RS by a factor of 2.
At very low source resistance (RS < 50 Ω), the voltage noise of the
amplifier dominates. As source resistance increases, the Johnson
noise of RS dominates until a higher resistance of RS > 2 kΩ is
achieved; the current noise component is larger than the
resistor noise.
00846-
033
100
1
0.1
10
100
1000
10000
SOURCE RESIST
ANCE ()
N
OIS
E(
nV
/√
H
z)
TOTAL NOISE
RESISTOR
NOISE
ONLY
Figure 34. Noise vs. Source Resistance
The AD797 is the optimum choice for low noise performance if
the source resistance is kept <1 kΩ. At higher values of source
resistance, optimum performance with respect to only noise is
obtained with other amplifiers from Analog Devices (Table 5).
For up to date information, see AN-940 at www.analog.com.
Table 5. Recommended Amplifiers for Different Source
Impedances
RS (k)
Recommended Amplifier
0 to <1
1 to <10
10 to <100
>100
LOW FREQUENCY NOISE
Analog Devices specifies low frequency noise as a peak-to-peak
quantity in a 0.1 Hz to 10 Hz bandwidth. Several techniques can
be used to make this measurement. The usual technique involves
amplifying, filtering, and measuring the amplifier noise for a
predetermined test time. The noise bandwidth of the filter is
corrected for, and the test time is carefully controlled because
the measurement time acts as an additional low frequency roll-off.
The plot in Figure 6 uses a slightly different technique: an FFT-
based instrument (Figure 35) is used to generate a 10 Hz brickwall
filter. A low frequency pole at 0.1 Hz is generated with an external
ac coupling capacitor, which is also the instrument being dc coupled.
Several precautions are necessary to attain optimum low
frequency noise performance:
Care must be used to account for the effects of RS. Even
a 10 Ω resistor has 0.4 nV/√Hz of noise (an error of 9%
when root sum squared with 0.9 nV/√Hz).
The test setup must be fully warmed up to prevent eOS drift
from erroneously contributing to input noise.
Circuitry must be shielded from air currents. Heat flow out
of the package through its leads creates the opportunity for
a thermoelectric potential at every junction of different metals.
Selective heating and cooling of these by random air currents
appears as 1/f noise and obscures the true device noise.
The results must be interpreted using valid statistical
techniques.
7
4
6
2
3
HP 3465
DYNAMIC SIGNAL
ANALYZER
(10Hz)
1
100k
*
VOUT
+VS
–VS
1.5F
AD797
00846-
034
*USE THE POWER SUPPLY BYPASSING SHOWN IN FIGURE 35.
Figure 35. Test Setup for Measuring 0.1 Hz to 10 Hz Noise
WIDEBAND NOISE
Due to its single-stage design, the noise of the AD797 is flat
over frequencies from less than 10 Hz to beyond 1 MHz. This
is not true of most dc precision amplifiers, where second-stage
noise contributes to input-referred noise beyond the audio
frequency range. The AD797 offers new levels of performance in
wideband imaging applications. In sampled data systems, where
aliasing of out-of-band noise into the signal band is a problem,
the AD797 outperforms all previously available IC op amps.
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相關代理商/技術參數 |
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| AD797BRZ-REEL7 | 功能描述:IC OPAMP GP 110MHZ ULDIST 8SOIC RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:2,500 系列:Excalibur™ 放大器類型:J-FET 電路數:1 輸出類型:- 轉換速率:45 V/µs 增益帶寬積:10MHz -3db帶寬:- 電流 - 輸入偏壓:20pA 電壓 - 輸入偏移:490µV 電流 - 電源:1.7mA 電流 - 輸出 / 通道:48mA 電壓 - 電源，單路/雙路(±):4.5 V ~ 38 V，±2.25 V ~ 19 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應商設備封裝:8-SOIC 包裝:帶卷 (TR) |
| AD797SQ/883B | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
| AD7980 | 制造商:AD 制造商全稱:Analog Devices 功能描述:16-bit, 1 MSPS PulSAR ADC in MSOP/QFN |
| AD7980_13 | 制造商:AD 制造商全稱:Analog Devices 功能描述:16-Bit, 1 MSPS PulSAR ADC in MSOP/QFN |
| AD79801 | 制造商:AD 制造商全稱:Analog Devices 功能描述:14-Bit, 500 kSPS PulSAR ADC in MSOP |
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