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| 型號： | AD797AR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 運動控制電子 |
| 英文描述： | Ultralow Distortion, Ultralow Noise Op Amp |
| 中文描述： | OP-AMP, 180 uV OFFSET-MAX, 110 MHz BAND WIDTH, PDSO8 |
| 封裝： | MS-012AA, SOIC-8 |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 406K |
| 代理商： | AD797AR |
AD797
REV. C
–9–
NOISE AND SOURCE IMPE DANCE CONSIDE RAT IONS
T he AD797’s ultralow voltage noise of 0.9 nV/
√
Hz
is achieved
with special input transistors running at nearly 1 mA of collector
current. It is important then to consider the total input referred
noise (
e
N
total
), which includes contributions from voltage noise
(
e
N
), current noise (
i
N
), and resistor noise (
√
4 kTr
S
).
e
N
total =
[
e
N
2
+
4
kTr
S
+
4
(
i
N
r
S
)
2
]
l/2
where
r
S
= total input source resistance.
T his equation is plotted for the AD797 in Figure 30. Since opti-
mum dc performance is obtained with matched source resis-
tances, this case is considered even though it is clear from
Equation 1 that eliminating the balancing source resistance will
lower the total noise by reducing the total r
S
by a factor of two.
At very low source resistance (r
S
<50
), the amplifiers’ voltage
noise dominates. As source resistance increases the Johnson
noise of r
S
dominates until at higher resistances (r
S
>2 k
) the
current noise component is larger than the resistor noise.
Equation 1
100
1
0.1
10
10
100
SOURCE RESISTANCE –
1000
10000
N
H
TOTAL NOISE
RESISTOR
NOISE
ONLY
Figure 30. Noise vs. Source Resistance
T he AD797 is the optimum choice for low noise performance
provided the source resistance is kept <1 k
. At higher values of
source resistance, optimum performance with respect to noise
alone is obtained with other amplifiers from Analog Devices (see
T able I).
T able I. Recommended Amplifiers for Different Source
Impedances
r
S
, ohms
Recommended Amplifier
0 to <1 k
1 k to <10 k
10 k to <100 k
>100 k
AD797
AD707, AD743/AD745, OP27/OP37, OP07
AD705, AD743/AD745, OP07
AD548, AD549, AD645, AD711, AD743/
AD745
LOW FRE QUE NCY NOISE
Analog Devices specifies low frequency noise as a peak to peak
(p-p) quantity in a 0.1 Hz to 10 Hz bandwidth. Several tech-
niques can be used to make this measurement. T he usual tech-
nique involves amplifying, filtering, and measuring the amplifiers
noise for a predetermined test time. T he noise bandwidth of the
filter is corrected for and the test time is carefully controlled
since the measurement time acts as an additional low frequency
roll-off.
T he plot in Figure 4 was made using a slightly different tech-
nique. Here an FFT based instrument (Figure 31) 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, the
instrument being dc coupled.
Several precautions are necessary to get optimum low frequency
noise performance:
1. Care must be used to account for the effects of r
S
, even a
10
resistor has 0.4 nV/
√
Hz
of noise (an error of 9% when
root sum squared with 0.9 nV/
√
Hz
).
2. T he test set up must be fully warmed up to prevent e
OS
drift
from erroneously contributing to input noise.
3. 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
will appear as 1/f noise and obscure the true device noise.
4. T he results must be interpreted using valid statistical
techniques.
100k
1.5
μ
F
1
HP 3465
DYNAMIC SIGNAL
ANALYZER
(10Hz)
V
OUT
** USE POWER SUPPLY BYPASSING SHOWN IN FIGURE 32.
AD797
**
2
7
3
4
6
**
–V
S
+V
S
Figure 31. Test Setup for Measuring 0.1 Hz to 10 Hz Noise
WIDE BAND NOISE
T he AD797, due to its single stage design, has the property that
its noise is flat over frequencies from less than 10 Hz to beyond
1 MHz. T his is not true of most dc precision amplifiers where
second stage noise contributes to input referred noise beyond
the audio frequency range. T he AD797 offers new levels of per-
formance in wideband imaging applications. In sampled data
systems, where aliasing of out of band noise into the signal band
is a problem, the AD797 will out perform all previously avail-
able IC op amps.
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| AD797BN | Ultralow Distortion, Ultralow Noise Op Amp |
| AD797BR | Ultralow Distortion, Ultralow Noise Op Amp |
| AD797AR-REEL | Ultralow Distortion, Ultralow Noise Op Amp |
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| AD797AR-REEL | 功能描述:IC OPAMP GP 110MHZ ULDIST 8SOIC RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標(biāo)準(zhǔn)包裝:150 系列:- 放大器類型:音頻 電路數(shù):2 輸出類型:- 轉(zhuǎn)換速率:5 V/µs 增益帶寬積:12MHz -3db帶寬:- 電流 - 輸入偏壓:100nA 電壓 - 輸入偏移:500µV 電流 - 電源:6mA 電流 - 輸出 / 通道:50mA 電壓 - 電源，單路/雙路(±):4 V ~ 32 V，±2 V ~ 16 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:8-TSSOP 包裝:管件 |
| AD797AR-REEL7 | 功能描述:IC OPAMP GP 110MHZ ULDIST 8SOIC RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標(biāo)準(zhǔn)包裝:150 系列:- 放大器類型:音頻 電路數(shù):2 輸出類型:- 轉(zhuǎn)換速率:5 V/µs 增益帶寬積:12MHz -3db帶寬:- 電流 - 輸入偏壓:100nA 電壓 - 輸入偏移:500µV 電流 - 電源:6mA 電流 - 輸出 / 通道:50mA 電壓 - 電源，單路/雙路(±):4 V ~ 32 V，±2 V ~ 16 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:8-TSSOP 包裝:管件 |
| AD797ARZ | 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(biāo)準(zhǔn)包裝:1 系列:MicroAmplifier™ 放大器類型:通用 電路數(shù):4 輸出類型:- 轉(zhuǎn)換速率:3.5 V/µs 增益帶寬積:1MHz -3db帶寬:- 電流 - 輸入偏壓:5pA 電壓 - 輸入偏移:1500µV 電流 - 電源:220µA 電流 - 輸出 / 通道:60mA 電壓 - 電源，單路/雙路(±):4.5 V ~ 36 V，±2.25 V ~ 18 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:14-SOIC 包裝:剪切帶 (CT) 其它名稱:296-29363-1 |
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| AD797ARZ-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(biāo)準(zhǔn)包裝:150 系列:- 放大器類型:音頻 電路數(shù):2 輸出類型:- 轉(zhuǎn)換速率:5 V/µs 增益帶寬積:12MHz -3db帶寬:- 電流 - 輸入偏壓:100nA 電壓 - 輸入偏移:500µV 電流 - 電源:6mA 電流 - 輸出 / 通道:50mA 電壓 - 電源，單路/雙路(±):4 V ~ 32 V，±2 V ~ 16 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:8-TSSOP 包裝:管件 |
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