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參數資料
| 型號： | AD8132ARMZ-REEL7 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Low Cost, High Speed Differential Amplifier |
| 中文描述： | 1 CHANNEL, VIDEO AMPLIFIER, PDSO8 |
| 封裝： | ROHS COMPLIANT, MO-187AA, MSOP-8 |
| 文件頁數： | 21/32頁 |
| 文件大小： | 456K |
| 代理商： | AD8132ARMZ-REEL7 |
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AD8132
THEORY OF OPERATION
The AD8132 differs from conventional op amps by the external
presence of an additional input and output. The additional input,
V
OCM
, controls the output common-mode voltage. The additional
output is the analog complement of the single output of a conven-
tional 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.
Rev. F | Page 21 of 32
One of the feedback loops controls the output common-mode
voltage, V
OUT, cm
. Its input is V
OCM
(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: V
OUT, cm
= V
OCM
.
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 R
G
of the input
that is not driven is tied to a reference voltage. This is ground.
Other conditions are discussed in the following sections. In
addition, the voltage at V
OCM
, and therefore V
OUT, 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
(
F1
G1
G1
R
R
R
β1
(
F2
G2
G2
R
R
R
β2
)
)
+
=
+
=
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):
(
(
β2
β1
+
)
)
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. Thus, +V
OUT
is equal to V
IN
,
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.
V
OCM
is assumed to be at midsupply. Because there is still the
constraint that +V
OUT
must equal V
IN
, changing the V
OCM
voltage
does not change +V
OUT
(equal to V
IN
). Therefore, the effect of
changing V
OCM
must show up at OUT.
For example, if V
OCM
is raised by 1 V, then V
OUT
must increase
by 2 V This makes V
OUT, 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 V
OCM
to the differential output is 2.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD8132ARMZ-REEL71 | 制造商:AD 制造商全稱: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 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:50 系列:LinCMOS™ 放大器類型:通用 電路數:4 輸出類型:- 轉換速率:0.05 V/µs 增益帶寬積:110kHz -3db帶寬:- 電流 - 輸入偏壓:0.7pA 電壓 - 輸入偏移:210µV 電流 - 電源:57µA 電流 - 輸出 / 通道:30mA 電壓 - 電源，單路/雙路(±):3 V ~ 16 V，±1.5 V ~ 8 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應商設備封裝:14-SOIC 包裝:管件 產品目錄頁面:865 (CN2011-ZH PDF) 其它名稱:296-1834296-1834-5 |
| AD8132AR-REEL7 | 功能描述:IC AMP DIFF LDIST LP 70MA 8SOIC RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:50 系列:LinCMOS™ 放大器類型:通用 電路數:4 輸出類型:- 轉換速率:0.05 V/µs 增益帶寬積:110kHz -3db帶寬:- 電流 - 輸入偏壓:0.7pA 電壓 - 輸入偏移:210µV 電流 - 電源:57µA 電流 - 輸出 / 通道:30mA 電壓 - 電源，單路/雙路(±):3 V ~ 16 V，±1.5 V ~ 8 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應商設備封裝:14-SOIC 包裝:管件 產品目錄頁面:865 (CN2011-ZH PDF) 其它名稱:296-1834296-1834-5 |
| AD8132ARZ | 功能描述:IC AMP DIFF LDIST LP 70MA 8SOIC RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 產品培訓模塊:Differential Circuit Design Techniques for Communication Applications 標準包裝:1 系列:- 放大器類型:RF/IF 差分 電路數:1 輸出類型:差分 轉換速率:9800 V/µs 增益帶寬積:- -3db帶寬:2.9GHz 電流 - 輸入偏壓:3µA 電壓 - 輸入偏移:- 電流 - 電源:40mA 電流 - 輸出 / 通道:- 電壓 - 電源，單路/雙路(±):3 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-VQFN 裸露焊盤，CSP 供應商設備封裝:16-LFCSP-VQ 包裝:剪切帶 (CT) 產品目錄頁面:551 (CN2011-ZH PDF) 其它名稱:ADL5561ACPZ-R7CT |
| AD8132ARZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Cost, High Speed Differential Amplifier |
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