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| 型号： | AD8132ARMZ-REEL |
| 厂商： | Analog Devices Inc |
| 文件页数： | 16/33页 |
| 文件大小： | 0K |
| 描述： | IC AMP DIFF LDIST LP 70MA 8MSOP |
| 标准包装： | 3,000 |
| 放大器类型： | 差分 |
| 电路数： | 1 |
| 输出类型： | 差分 |
| 转换速率： | 1200 V/µs |
| -3db带宽： | 360MHz |
| 电流 - 输入偏压： | 3µA |
| 电压 - 输入偏移： | 1000µV |
| 电流 - 电源： | 12mA |
| 电流 - 输出 / 通道： | 70mA |
| 电压 - 电源，单路/双路(±)： | 2.7 V ~ 11 V，±1.35 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-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 8-MSOP |
| 包装： | 带卷 (TR) |
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AD8132
Rev. I | Page 22 of 32
THEORY OF OPERATION
The AD8132 differs from conventional op amps by the external
presence of an additional input and output. The additional
input, VOCM, controls the output common-mode voltage. The
additional output is the analog complement of the single output
of a conventional op amp. For its operation, the AD8132 uses two
feedback loops as compared to the single loop of conventional
op amps. Although this provides significant freedom to create
various novel circuits, basic op amp theory can still be used to
analyze the operation.
One of the feedback loops controls the output common-mode
voltage, VOUT, cm. Its input is VOCM (Pin 2) and the output is the
common mode, or average voltage, of the two differential outputs
(+OUT and OUT). The gain of this circuit is internally set to
unity. When the AD8132 is operating in its linear region, this
establishes one of the operational constraints: VOUT, cm = VOCM.
The second feedback loop controls the differential operation.
Similar to an op amp, the gain and gain shaping of the transfer
function can be controlled by adding passive feedback networks.
However, only one feedback network is required to close the
loop and fully constrain the operation, but depending on the
function desired, two feedback networks can be used. This is
possible because there are two outputs that are each inverted
with respect to the differential inputs.
GENERAL USAGE OF THE AD8132
Several assumptions are made here for a first-order analysis; they
are the typical assumptions used for the analysis of op amps.
The input bias currents are sufficiently small so they can be
neglected.
The output impedances are arbitrarily low.
The open-loop gain is arbitrarily large and drives the
amplifier to a state where the input differential voltage is
effectively 0.
Offset voltages are assumed to be 0.
Though it is possible to operate the AD8132 with a purely
differential input, many of its applications call for a circuit
that has a single-ended input with a differential output.
For a single-ended-to-differential circuit, the RG of the input that
is not driven is tied to a reference voltage or to ground. Additional
conditions are discussed in the following sections. In addition,
the voltage at VOCM, and therefore VOUT,cm, is assumed to be ground.
Figure 67 shows a generalized schematic of such a circuit using an
AD8132 with two feedback paths.
For each feedback network, a feedback factor can be defined as
the fraction of the output signal that is fed back to the opposite
sign input. These terms are
β1 = RG1/(RG1 + RF1)
β2 = RG2/(RG2 + RF2)
The feedback factor, β1, is for the side that is driven, and the
feedback factor, β2, is for the side that is tied to a reference
voltage (ground). Note that each feedback factor can vary
anywhere between 0 and 1.
A single-ended-to-differential gain equation can be derived
(this is true for all values of β1 and β2) from
(
)
()
β2
β1
G
+
=
1
2
This expression is not very intuitive, but some further examples
can provide better understanding of its implications. One
observation that can be made immediately is that a tolerance
error in β1 does not have the same effect on gain as the same
tolerance error in β2.
DIFFERENTIAL AMPLIFIER WITHOUT RESISTORS
(HIGH INPUT IMPEDANCE INVERTING AMPLIFIER)
The simplest closed-loop circuit that can be made does not
require any resistors and is shown in Figure 70. In this circuit,
β1 is equal to 0, and β2 is equal to 1. The gain is equal to 2.
A more intuitive method to figure the gain is by simple inspection.
+OUT is connected to IN, whose voltage is equal to the voltage at
+IN under equilibrium conditions. Therefore, +VOUT is equal to
VIN, and there is unity gain in this path. Because OUT has to
swing in the opposite direction from +OUT due to the common-
mode constraint, its effect doubles the output signal and
produces a gain of 2.
One useful function that this circuit provides is a high input
impedance inverter. If +OUT is ignored, there is a unity-gain,
high input impedance amplifier formed from +IN to OUT.
Most traditional op amp inverters have relatively low input
impedances, unless they are buffered with another amplifier.
VOCM is assumed to be at midsupply. Because there is still the
constraint that +VOUT must equal VIN, changing the VOCM voltage
does not change +VOUT (equal to VIN). Therefore, the effect of
changing VOCM must show up at OUT.
For example, if VOCM is raised by 1 V, then VOUT must increase
by 2 V. This makes VOUT,cm also increase by 1 V because it is defined
as the average of the two differential output voltages. This means
that the gain from VOCM to the differential output is 2.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8132ARMZ-REEL1 | 制造商:AD 制造商全称:Analog Devices 功能描述:Low Cost, High Speed Differential Amplifier |
| AD8132ARMZ-REEL7 | 功能描述:IC AMP DIFF LDIST LP 70MA 8MSOP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 产品培训模块:Differential Circuit Design Techniques for Communication Applications 标准包装:1 系列:- 放大器类型:RF/IF 差分 电路数:1 输出类型:差分 转换速率:9800 V/µs 增益带宽积:- -3db带宽:2.9GHz 电流 - 输入偏压:3µA 电压 - 输入偏移:- 电流 - 电源:40mA 电流 - 输出 / 通道:- 电压 - 电源，单路/双路(±):3 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:16-VQFN 裸露焊盘，CSP 供应商设备封装:16-LFCSP-VQ 包装:剪切带 (CT) 产品目录页面:551 (CN2011-ZH PDF) 其它名称:ADL5561ACPZ-R7CT |
| AD8132ARMZ-REEL71 | 制造商:AD 制造商全称:Analog Devices 功能描述:Low Cost, High Speed Differential Amplifier |
| AD8132AR-REEL | 功能描述:IC AMP DIFF LDIST LP 70MA 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 |
| AD8132AR-REEL7 | 功能描述:IC AMP DIFF LDIST LP 70MA 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 |
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