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參數(shù)資料
| 型號： | AD7837 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Complete, Dual 12-Bit MDACs(完備的雙12位乘法D/A轉(zhuǎn)換器) |
| 中文描述： | 完備的雙12位醫(yī)療儀器行政管理制度（完備的雙12位乘法的D / A轉(zhuǎn)換器） |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 280K |
| 代理商： | AD7837 |
AD7837/AD7847
REV. 0
–9–
APPLICAT IONS
PROGRAMMABLE GAIN AMPLIFIE R (PGA)
T he dual DAC/amplifier combination along with access to R
FB
make the AD7837 ideal as a programmable gain amplifier. In
this application, the DAC functions as a programmable resistor
in the amplifier feedback loop. T his type of configuration is
shown in Figure 8 and is suitable for ac gain control. T he cir-
cuit consists of two PGAs in series. Use of a dual configuration
provides greater accuracy over a wider dynamic range than a
single PGA solution. T he overall system gain is the product of
the individual gain stages. T he effective gains for each stage are
controlled by the DAC codes. As the code decreases, the effec-
tive DAC resistance increases, and so the gain also increases.
DAC A
DAC B
2
5
10
8
9
3
4
12
R
FBA
AGNDA
AD7837
V
REFB
V
OUTB
V
OUT
V
IN
V
REFA
V
OUTA
R
FBB
AGNDB
Figure 8. Dual PGA Circuit
T he transfer function is given by
V
OUT
V
IN
=
R
EQA
R
FBA
×
R
EQB
R
FBB
(1)
where
R
EQA
,
R
EQB
are the effective DAC resistances controlled
by the digital input code:
R
EQ
=
2
12
R
IN
N
(2)
where
R
IN
is the DAC input resistance and is equal to R
FB
and
N
= DAC input code in decimal.
T he transfer function in (1) thus simplifies to
V
OUT
V
IN
=
2
12
N
A
×
2
12
N
B
(3)
where
N
A
= DAC A input code in decimal and
N
B
= DAC B
input code in decimal.
N
A
, N
B
may be programmed between 1 and (2
12
–1). T he zero
code is not allowed as it results in an open loop amplifier re-
sponse. T o minimize errors, the digital codes N
A
and N
B
should be chosen to be equal to or as close as possible to each
other to achieve the required gain.
BIPOLAR OPE RAT ION
(4-QUADRANT MULT IPLICAT ION)
Figure 7 shows the AD7837/AD7847 connected for bipolar op-
eration. T he coding is offset binary as shown in T able IV. When
V
IN
is an ac signal, the circuit performs 4-quadrant multiplica-
tion. T o maintain the gain error specifications, resistors R1, R2
and R3 should be ratio matched to 0.01%. Note that on the
AD7847 the feedback resistor R
FB
is internally connected to
V
OUT
.
AD7837
AD7847
AD711
R1
20k
DAC A
*
AGNDA
DGND
*
INTERNALLY
CONNECTED
ON AD7847
V
SS
V
OUTA
V
OUT
R
FBA
V
DD
V
REFA
V
DD
V
IN
V
SS
R2
20k
R3
10k
Figure 7. Bipolar Offset Binary Operation
T able IV. Bipolar Code T able
DAC Latch Contents
MSB LSB
Analog Output, V
OUT
1111 1111 1111
+
V
IN
×
2047
2048
1000 0000 0001
0 V
+
V
IN
×
1
2048
1000 0000 0000
0111 1111 1111
±
V
IN
×
1
2048
0000 0000 0000
±
V
IN
×
2048
2048
=
±
V
IN
Note 1 LSB =
V
IN
2048
.
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| AD7837AN | 功能描述:IC DAC 12BIT MULT DUAL 24-DIP RoHS:否 類別:集成電路 (IC) >> 數(shù)據(jù)采集 - 數(shù)模轉(zhuǎn)換器 系列:- 產(chǎn)品培訓(xùn)模塊:Data Converter Fundamentals DAC Architectures 標(biāo)準(zhǔn)包裝:750 系列:- 設(shè)置時(shí)間:7µs 位數(shù):16 數(shù)據(jù)接口:并聯(lián) 轉(zhuǎn)換器數(shù)目:1 電壓電源:雙 ± 功率耗散（最大）:100mW 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:28-LCC（J 形引線） 供應(yīng)商設(shè)備封裝:28-PLCC（11.51x11.51） 包裝:帶卷 (TR) 輸出數(shù)目和類型:1 電壓，單極；1 電壓，雙極 采樣率（每秒）:143k |
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| AD7837AN883B | 制造商:AD 制造商全稱:Analog Devices 功能描述:LC2MOS Complete, Dual 12-Bit MDACs |
| AD7837AN-883B | 制造商:AD 制造商全稱:Analog Devices 功能描述:LC2MOS Complete, Dual 12-Bit MDACs |
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