参数资料
| 型号： | AD8572AR |
| 厂商： | Analog Devices Inc |
| 文件页数： | 7/24页 |
| 文件大小： | 0K |
| 描述： | IC OPAMP CHOPPER R-R DUAL 8SOIC |
| 标准包装： | 98 |
| 放大器类型： | 断路器（零漂移） |
| 电路数： | 2 |
| 输出类型： | 满摆幅 |
| 转换速率： | 0.4 V/µs |
| 增益带宽积： | 1.5MHz |
| 电流 - 输入偏压： | 10pA |
| 电压 - 输入偏移： | 1µV |
| 电流 - 电源： | 850µA |
| 电流 - 输出 / 通道： | 30mA |
| 电压 - 电源，单路/双路(±)： | 2.7 V ~ 5.5 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SO |
| 包装： | 管件 |
AD8571/AD8572/AD8574
Rev. E | Page 15 of 24
AUTO-ZERO PHASE
In this phase, all ΦAX switches are closed, and all ΦB switches
are open. Here, the nulling amplifier is taken out of the gain
loop by shorting its two inputs together. Of course, there is a
degree of offset voltage, shown as VOSA, inherent in the nulling
amplifier, that maintains a potential difference between the +IN
and IN inputs. The nulling amplifier feedback loop is closed
through ΦA2, and VOSA appears at the output of the nulling
amplifier and on CM1, an internal capacitor in the AD857x.
Mathematically, this can be expressed in the time domain as
VOA[t] = AAVOSA[t] BAVOA[t]
(1)
This can also be expressed as
[]
A
OSA
A
OA
B
t
V
A
t
V
+
=
1
(2)
The previous equations show that the offset voltage of the nulling
amplifier times a gain factor appears at the output of the nulling
amplifier and thus on the CM1 capacitor.
AMPLIFICATION PHASE
When the ΦB switches close and the ΦAX switches open for
the amplification phase, the offset voltage remains on CM1 and
essentially corrects any error from the nulling amplifier. The
voltage across CM1 is designated as VNA. The potential difference
between the two inputs to the primary amplifier is designated as
VIN, or VIN = (VIN+ VIN). The output of the nulling amplifier
can then be expressed as
VOA[t] = AA(VIN[t] VOSA[t]) BAVNA[t]
(3)
Because ΦAX is now open and there is no place for CM1 to
discharge, the voltage (VNA) at the present time (t) is equal to
the voltage at the output of the nulling amp (VOA) at the time when
ΦAX is closed. If the period of the autocorrection switching
frequency is designated as TS, the amplifier switches between
phases every 0.5 × TS. Therefore, in the amplification phase
[]
=
S
NA
T
t
V
t
V
2
1
(4)
and substituting Equation 4 and Equation 2 into Equation 3 yields
[]
[ ]
A
S
OSA
A
OSA
A
IN
A
OA
B
T
t
V
B
A
t
V
A
t
V
A
t
V
+
+
=
1
2
1
(5)
For the sake of simplification, it can be assumed that the auto-
correction frequency is much faster than any potential change
in VOSA or VOSB. This is a good assumption because changes in
offset voltage are a function of temperature variation or long-
term wear time, both of which are much slower than the
auto-zero clock frequency of the AD857x, which effectively
makes the VOS time invariant, and Equation 5 can be rewritten as
[]
[ ]
(
)
A
OSA
A
OSA
A
IN
A
OA
B
V
B
A
V
B
A
t
V
A
t
V
+
+
=
1
(6)
or
[]
[ ]
+
=
A
OSA
IN
A
OA
B
V
t
V
A
t
V
1
(7)
Here, the auto-zeroing becomes apparent. Note that the VOS
term is reduced by a factor of 1 + BA, which shows how the
nulling amplifier has greatly reduced its own offset voltage error
even before correcting the primary amplifier. Therefore, the
primary amplifier output voltage is the voltage at the output of the
AD857x amplifier. It is equal to
VOUT[t] = AB(VIN[t] + VOSB) + BBVNB
(8)
In the amplification phase, VOA = VNB, so this can be rewritten as
[ ]
[]
+
=
A
OSA
IN
A
B
OSB
B
IN
B
OUT
B
V
t
V
A
B
V
A
t
V
A
t
V
1
(9)
Combining terms yield
[ ]
[]
()
OSB
B
A
OSA
B
A
B
A
B
IN
OUT
V
A
B
V
B
A
B
A
t
V
t
V
+
=
1
(10)
The AD857x architecture is optimized in such a way that
AA = AB, BA = BB, and BA >> 1. In addition, the gain product to
AABB is much greater than AB. Therefore, Equation 10 can be
simplified to
VOUT[t] = VIN[t]AABA + AA(VOSA+ VOSB)
(11)
Most obvious is the gain product of both the primary and nulling
amplifiers. This AABA term is what gives the AD857x its extremely
high open-loop gain. To understand how VOSA and VOSB relate to
the overall effective input offset voltage of the complete amplifier,
set up the generic amplifier equation of
VOUT = k × (VIN + VOS, EFF)
(12)
where:
k is the open-loop gain of an amplifier.
VOS, EFF is its effective offset voltage.
Putting Equation 12 into the form of Equation 11 gives
VOUT[t] = VIN[t]AABA + VOS, EFFAABA
(13)
相关PDF资料 |
PDF描述 |
|---|---|
| Y16245K00000T9R | RES 5.0K OHM .2W .01% FOIL 0805 |
| 86453-110LF | MINITEK II R/A HDR |
| LT6203IDD#TRPBF | IC OP AMP DUAL 100MHZ 3MA 8-DFN |
| 86453-110 | MINITEK II R/A HDR |
| TMM-135-01-S-S-SM | CONN HEADER 35POS SNGL 2MM SMD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8572ARMZ-REEL | 制造商:AD 制造商全称:Analog Devices 功能描述:Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8572AR-REEL | 功能描述:IC OPAMP CHOPPER R-R DUAL 8SOIC RoHS:否 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:50 系列:LinCMOS™ 放大器类型:通用 电路数:4 输出类型:- 转换速率:0.05 V/µs 增益带宽积:110kHz -3db带宽:- 电流 - 输入偏压:0.7pA 电压 - 输入偏移:210µV 电流 - 电源:57µA 电流 - 输出 / 通道:30mA 电压 - 电源，单路/双路(±):3 V ~ 16 V，±1.5 V ~ 8 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商设备封装:14-SOIC 包装:管件 产品目录页面:865 (CN2011-ZH PDF) 其它名称:296-1834296-1834-5 |
| AD8572AR-REEL7 | 功能描述:IC OPAMP CHOPPER R-R DUAL 8SOIC RoHS:否 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:1 系列:- 放大器类型:通用 电路数:4 输出类型:满摆幅 转换速率:0.6 V/µs 增益带宽积:1MHz -3db带宽:- 电流 - 输入偏压:2pA 电压 - 输入偏移:1000µV 电流 - 电源:85µA 电流 - 输出 / 通道:20mA 电压 - 电源，单路/双路(±):1.8 V ~ 6 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:14-SOIC（0.154"，3.90mm 宽） 供应商设备封装:14-SOICN 包装:剪切带 (CT) 产品目录页面:680 (CN2011-ZH PDF) 其它名称:MCP6L04T-E/SLCT |
| AD8572ARU | 制造商:Analog Devices 功能描述:SP Amp Chopper Stabilization Dual R-R I/O 5V 8-Pin TSSOP Tube 制造商:Rochester Electronics LLC 功能描述:DUAL PRECISION RAIL-RAIL CHOPPER OPAMP - Bulk 制造商:Analog Devices 功能描述:IC OP-AMP DUAL R/R |
| AD8572ARU-REEL | 制造商:Analog Devices 功能描述:SP Amp Chopper Stabilization Dual R-R I/O 5V 8-Pin TSSOP T/R |
发布紧急采购，3分钟左右您将得到回复。