- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄375234 > AD625 (Analog Devices, Inc.) Programmable Gain Instrumentation Amplifier(儀器用放大器) PDF資料下載
參數(shù)資料
| 型號(hào)： | AD625 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | Programmable Gain Instrumentation Amplifier(儀器用放大器) |
| 中文描述： | 可編程增益儀表放大器（儀器用放大器） |
| 文件頁(yè)數(shù)： | 12/14頁(yè) |
| 文件大?。?/td> | 549K |
| 代理商： | AD625 |
第1頁(yè)第2頁(yè)第3頁(yè)第4頁(yè)第5頁(yè)第6頁(yè)第7頁(yè)第8頁(yè)第9頁(yè)第10頁(yè)第11頁(yè)當(dāng)前第12頁(yè)第13頁(yè)第14頁(yè)
AD625
REV. B
–12–
Figure 39. SPGA with Multiplexer Error Sources
Figure 39 shows a complete SPGA feeding a 12-bit DAS with a
0 V–10 V input range. This configuration was used in the error
budget analysis shown in Table II. The gain used for the RTI
calculations is set at 16. As the gain is changed, the ON resis-
tance of the multiplexer and the feedback resistance will change,
which will slightly alter the values in the table.
Table II. Errors Induced by Multiplexer to an SPGA
Induced
Error
Specifications
AD625C
Voltage Offset
Calculation
AD7520KN
Induced RTI
RTI Offset
Voltage
Gain Sense Switch
Offset
Current
40 nA
40 nA
×
170
=
6.8
μ
V
6.8
μ
V
Resistance
170
RTI Offset
Voltage
Gain Sense Differential
Current
60 nA
60 nA
×
6.8
=
0.41
μ
V
0.41
μ
V
Switch
Resistance
6.8
RTO Offset
Voltage
Feedback
Resistance Leakage
20 k
1
Differential
2 (0.2 nA
×
20 k
)
= 8
μ
V/16
0.5
μ
V
Current (I
S
)
2
+0.2 nA
–0.2 nA
RTO Offset
Voltage
Feedback
Resistance Leakage
20 k
1
Differential
2 (1 nA
×
20 k
)
= 40
μ
V/16
2.5
μ
V
Current
(I
)
2
+1 nA
–1 nA
Total error induced by a typical CMOS multiplexer
to an SPGA at 25
°
C
10.21
m
A
NOTES
1
The resistor for this calculation is the user provided feedback resistance (R
).
20 k
is recommended value (see Resistor Programmable Gain Amplifier section).
2
The leakage currents (I
S
and I
OUT
) will induce an offset voltage, however, the offset
will be determined by the difference between the leakages of each “half’’ of the dif-
ferential multiplexer. The differential leakage current is multiplied by the feedback
resistance (see Note 1), to determine offset voltage. Because differential leakage
current is not a parameter specified on multiplexer data sheets, the most extreme
difference (one most positive and one most negative) was used for the calculations
in Table II. Typical performance will be much better.
*
*The frequency response and settling will be affected by the ON resistance and
internal capacitance of the multiplexer. Figure 40 shows the settling time vs.
ON resistance at different gain settings for an AD625 based SPGA.
**Switch resistance and leakage current errors can be reduced by using relays.
These capacitances may also be incorporated as part of the ex-
ternal input protection circuit (see section on Input Protection).
As a general practice every effort should be made to match the
extraneous capacitance at Pins 15 and 2, and Pins 1 and 16, to
preserve high ac CMR.
SOFTWARE PROGRAMMABLE GAIN AMPLIFIER
An SPGA provides the ability to externally program precision
gains from digital inputs. Historically, the problem in systems
requiring electronic switching of gains has been the ON resis-
tance (R
ON
) of the multiplexer, which appears in series with the
gain setting resistor R
G
. This can result in substantial gain errors
and gain drifts. The AD625 eliminates this problem by making
the gain drive and gain sense pins available (Pins 2, 15, 5, 12;
see Figure 39). Consequently the multiplexer’s ON resistance is
removed from the signal current path. This transforms the ON
resistance error into a small nullable offset error. To clarify this
point, an error budget analysis has been performed in Table II
based on the SPGA configuration shown in Figure 39.
Figure 38. SPGA in a Gain of 16
Figure 38 shows an AD625 based SPGA with possible gains of
1, 4, 16, 64. R
G
equals the resistance between the gain sense
lines (Pins 2 and 15) of the AD625. In Figure 38, R
G
equals
the sum of the two 975
resistors and the 650
resistor, or
2600
. R
F
equals the resistance between the gain sense and the
gain drive pins (Pins 12 and 15, or Pins 2 and 5), that is R
F
equals the 15.6 k
resistor plus the 3.9 k
resistor, or 19.5 k
.
The gain, therefore equals:
2
R
F
R
G
+
1
=
2(19.5
k
)
(2.6
k
)
+
1
=
16
As the switches of the differential multiplexer proceed synchro-
nously, R
G
and R
F
change, resulting in the various programmed
gain settings.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD628ARMZ | High Common-Mode Voltage, Programmable Gain Difference Amplifier |
| AD628ARMZ-R7 | High Common-Mode Voltage, Programmable Gain Difference Amplifier |
| AD628ARMZ-RL | High Common-Mode Voltage, Programmable Gain Difference Amplifier |
| AD628ARZ | High Common-Mode Voltage, Programmable Gain Difference Amplifier |
| AD628ARZ-R7 | High Common-Mode Voltage, Programmable Gain Difference Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD62501P | 制造商:TOSHIBA 制造商全稱:Toshiba Semiconductor 功能描述:7 SINGLE DRIVER |
| AD62550A | 制造商:ESMT 制造商全稱:Elite Semiconductor Memory Technology Inc. 功能描述:Class-D Audio Power Amplifier with USB / I2S Interface |
| AD62551A | 制造商:ESMT 制造商全稱:Elite Semiconductor Memory Technology Inc. 功能描述:USB controller with external Amplifier and Recording function |
| AD6255A | 制造商:ESMT 制造商全稱:Elite Semiconductor Memory Technology Inc. 功能描述:Class-D Audio Power Amplifier with USB / I2S Interface and Recording function |
| AD625A | 制造商:AD 制造商全稱:Analog Devices 功能描述:Programmable Gain Instrumentation Amplifier |
發(fā)布緊急采購(gòu)，3分鐘左右您將得到回復(fù)。