參數(shù)資料
| 型號： | AD625CDZ |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 4/15頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC AMP INST 25MHZ LN 16CDIP |
| 標準包裝： | 1 |
| 放大器類型： | 儀表 |
| 電路數(shù)： | 1 |
| 轉換速率： | 5 V/µs |
| 增益帶寬積： | 25MHz |
| -3db帶寬： | 650kHz |
| 電流 - 輸入偏壓： | 10nA |
| 電壓 - 輸入偏移： | 10µV |
| 電流 - 電源： | 3.5mA |
| 電壓 - 電源，單路/雙路(±)： | ±6 V ~ 18 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 通孔 |
| 封裝/外殼： | 16-CDIP（0.300"，7.62mm） |
| 供應商設備封裝： | 16-CDIP 側面銅焊 |
| 包裝： | 管件 |
AD625
REV. D
–12–
GROUND RETURNS FOR BIAS CURRENTS
Input bias currents are those currents necessary to bias the input
transistors of a dc amplifier. There must be a direct return path
for these currents, otherwise they will charge external capaci-
tances, causing the output to drift uncontrollably or saturate.
Therefore, when amplifying “floating” input sources such as
transformers, or ac-coupled sources, there must be a dc path
from each input to ground as shown in Figure 35.
AD625
+VS
–VS
RF
RG
RF
VOUT
LOAD
TO POWER
SUPPLY
GROUND
SENSE
REFERENCE
Figure 35a. Ground Returns for Bias Currents with
Transformer Coupled Inputs
AD625
+VS
–VS
RF
RG
RF
VOUT
LOAD
TO POWER
SUPPLY
GROUND
SENSE
REFERENCE
Figure 35b. Ground Returns for Bias Currents with
Thermocouple Input
AD625
+VS
–VS
RF
RG
RF
VOUT
LOAD
TO POWER
SUPPLY
GROUND
SENSE
REFERENCE
100k
Figure 35c. Ground Returns for Bias Currents with AC
Coupled Inputs
AUTOZERO CIRCUITS
In many applications it is necessary to maintain high accuracy.
At room temperature, offset effects can be nulled by the use of
offset trimpots. Over the operating temperature range, however,
offset nulling becomes a problem. For these applications the
autozero circuit of Figure 36 provides a hardware solution.
OTHER CONSIDERATIONS
One of the more overlooked problems in designing ultralow-
drift dc amplifiers is thermocouple induced offset. In a circuit
comprised of two dissimilar conductors (i.e., copper, kovar), a
current flows when the two junctions are at different tempera-
tures. When this circuit is broken, a voltage known as the
“Seebeck” or thermocouple emf can be measured. Standard IC
lead material (kovar) and copper form a thermocouple with a
high thermoelectric potential (about 35
V°C). This means that
care must be taken to insure that all connections (especially
those in the input circuit of the AD625) remain isothermal. This
includes the input leads (1, 16) and the gain sense lines (2, 15).
These pins were chosen for symmetry, helping to desensitize the
input circuit to thermal gradients. In addition, the user should
also avoid air currents over the circuitry since slowly fluctuating
AD625
+VS
–VS
AD7502
GND VDD VSS
15
16
13
14
VDD
VSS
GND
AD7510DIKD
A1
A2
A3
A4
200 s
ZERO PULSE
AD711
+
VIN
–
0.1 F LOW
LEAKAGE
1k
12
11
9
10 VOUT
Figure 36. Auto-Zero Circuit
thermocouple voltages will appear as “flicker” noise. In SPGA
applications relay contacts and CMOS mux leads are both
potential sources of additional thermocouple errors.
The base emitter junction of an input transistor can rectify out
of band signals (i.e., RF interference). When amplifying small
signals, these rectified voltages act as small dc offset errors. The
AD625 allows direct access to the input transistors’ bases and
emitters enabling the user to apply some first order filtering to
these unwanted signals. In Figure 37, the RC time constant
should be chosen for desired attenuation of the interfering signals.
In the case of a resistive transducer, the capacitance alone work-
ing against the internal resistance of the transducer may suffice.
+GAIN SENSE
+IN
–IN
RTI NULL
RTO
NULL
RTO
NULL
+V
+GAIN DRIVE
–GAIN DRIVE
RF
RG
RF
NC
REF
–VS
VOUT
+VS
A1
A2
AD625
10k
A3
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
FILTER
CAP
R
FILTER
CAP
C
–GAIN SENSE
+IN
SENSE
VOUT
–IN
Figure 37. Circuit to Attenuate RF Interference
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| AD625JNZ | 功能描述:IC AMP INST 25MHZ LN 16DIP RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:2,500 系列:- 放大器類型:通用 電路數(shù):4 輸出類型:- 轉換速率:0.6 V/µs 增益帶寬積:1MHz -3db帶寬:- 電流 - 輸入偏壓:45nA 電壓 - 輸入偏移:2000µV 電流 - 電源:1.4mA 電流 - 輸出 / 通道:40mA 電壓 - 電源，單路/雙路(±):3 V ~ 32 V，±1.5 V ~ 16 V 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:14-TSSOP（0.173"，4.40mm 寬） 供應商設備封裝:14-TSSOP 包裝:帶卷 (TR) 其它名稱:LM324ADTBR2G-NDLM324ADTBR2GOSTR |
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