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參數(shù)資料
| 型號(hào)： | AD621BR |
| 廠商： | ANALOG DEVICES INC |
| 元件分類(lèi)： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | Low Drift, Low Power Instrumentation Amplifier |
| 中文描述： | INSTRUMENTATION AMPLIFIER, 215 uV OFFSET-MAX, 0.2 MHz BAND WIDTH, PDSO8 |
| 封裝： | PLASTIC, SOIC-8 |
| 文件頁(yè)數(shù)： | 13/16頁(yè) |
| 文件大?。?/td> | 663K |
| 代理商： | AD621BR |
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AD621
REV. A
–13–
Precision V-I Converter
The AD621 along with another op amp and two resistors make
a precision current source (Figure 35). The op amp buffers the
reference terminal to maintain good CMR. The output voltage
V
X
of the AD621 appears across R1 which converts it to a cur-
rent. This current less only the input bias current of the op amp
then flows out to the load.
AD621
+V
S
–V
S
V
IN+
V
IN–
AD705
LOAD
R1
I
L
V
R1=
I =
(V ) – (V ) G
R1
3
7
6
5
4
2
+ V –
Figure 35. Precision Voltage to Current Converter
(Operates on 1.8 mA,
±
3 V)
INPUT AND OUTPUT OFFSET VOLTAGE
The AD621 is fully specified for total input errors at gains of 10
and 100. That is, effects of all error sources within the AD621
are properly included in the guaranteed input error specs, elimi-
nating the need for separate error calculation.
Total Error RTI
=
Input Error
+ (
Output Error/G
)
Total Error RTO
= (Input Error
×
G) +
Output Error
REFERENCE TERMINAL
Although usually grounded, the reference terminal may be used
to offset the output of the AD621. This is useful when the load
is “floating” or does not share a ground with the rest of the sys-
tem. It also provides a direct means of injecting a precise offset.
Another benefit of having a reference terminal is that it can be
quite effective in eliminating ground loops and noise in a circuit
or system.
7
4
6
5
3
2
AD621
R
P
R
P
V
OUT
V
OL
V
OL
GAIN = 10 OR 100
+V
S
–V
S
Figure 36. Input Overload Protection
INPUT OVERLOAD CONSIDERATIONS
Failure of a transducer, faults on input lines, or power supply
sequencing can subject the inputs of an instrumentation ampli-
fier to voltages well beyond their linear range, or even the supply
voltage, so it is essential that the amplifier handle these over-
loads without being damaged.
The AD621 will safely withstand continuous input overloads of
±
3.0 volts (
±
6.0 mA). This is true for gains of 10 and 100, with
power on or off.
The inputs of the AD621 are protected by high current capacity
dielectrically isolated 400
thin-film resistors R3 and R4 (Fig-
ure 29) and by diodes which protect the input transistors Q1
and Q2 from reverse breakdown. If reverse breakdown occurred,
there would be a permanent increase in the amplifier’s input
current.
The input overload capability of the AD621 can be easily in-
creased while only slightly degrading the noise, common-mode
rejection and offset drift of the device by adding external resis-
tors in series with the amplifier’s inputs as shown in Figure 36.
Table II summarizes the overload voltages and total input noise
for a range of range of r values. Note that a 2 k
resistor in se-
ries with each input will protect the AD621 from a
±
15 volt
continuous overload, while only increasing input noise to
13 nV
√
Hz
—about the same level as would be expected from a
typical unprotected 3 op amp in amp.
Table II. Input Overload Protection vs. Value of Resistor R
P
Total Input Noise
in nV
√
Hz
@ 1 kHz
Maximum Continuous
Overload Voltage, V
OL
In Volts
Value of
Resistor R
P
G = 10
G = 100
0
499
1.00 k
2.00 k
3.01 k
*
4.99 k
*
14
14
14
15
16
17
9
10
11
13
14
16
3
6
9
15
21
33
*1/4 watt, 1% metal-film resistor. All others are 1/8 watt, 1% RN55
or equivalent.
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| AD621BR-REEL | 功能描述:IC AMP INST LDRIFT LP 18MA 8SOIC RoHS:否 類(lèi)別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:Excalibur™ 放大器類(lèi)型:J-FET 電路數(shù):1 輸出類(lèi)型:- 轉(zhuǎn)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(lèi)型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:8-SOIC 包裝:帶卷 (TR) |
| AD621BR-REEL7 | 功能描述:IC AMP INST LDRIFT LP 18MA 8SOIC RoHS:否 類(lèi)別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:Excalibur™ 放大器類(lèi)型:J-FET 電路數(shù):1 輸出類(lèi)型:- 轉(zhuǎn)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(lèi)型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:8-SOIC 包裝:帶卷 (TR) |
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