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| 型號(hào)： | AD8132ARMZ |
| 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(shù)： | 22/32頁 |
| 文件大小： | 456K |
| 代理商： | AD8132ARMZ |
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AD8132
OTHER β2 = 1 CIRCUITS
The preceding simple configuration with β2 = 1 and its gain of
2 is the highest gain circuit that can be made under this condition.
Since β1 was equal to 0, only higher β1 values are possible. The
circuits with higher values of β1 have gains lower than 2. However,
circuits with β1 equal to 1 are not practical because they have
no effective input and result in a gain of 0.
Rev. F | Page 22 of 32
To increase β1 from 0, it is necessary to add two resistors in a feed-
back network. A generalized circuit that has β1 with a value higher
than 0 is shown in Figure 69. A couple of different convenient
gains that can be created are a gain of 1, when β1 is equal to 1/3,
and a gain of 0.5, when β1 equals 0.6.
With β2 equal to 1 in these circuits, V
OCM
serves as the refer-
ence voltage that measures the input voltage and the individual
output voltages. In general, when V
OCM
is varied in circuits
with unmatched feedback networks, a differential output
signal is generated that is proportional to the applied V
OCM
voltage.
VARYING β2
Though the β2 = 1 circuit sets β2 to 1, another class of simple
circuits can be made that sets β2 equal to 0. This means that
there is no feedback from +OUT to IN. This class of circuits
is very similar to a conventional inverting op amp. However,
the AD8132 circuits have an additional output and common-
mode input that can be analyzed separately (see Figure 71).
With IN connected to ground, +IN becomes a virtual ground
in the sense that the term is used for conventional op amps. Both
inputs must maintain the same voltage for equilibrium operation;
therefore, if one is set to ground, the other is driven to ground.
The input impedance can also be seen to be equal to R
G
, just as
in a conventional op amp.
In this case, however, the positive input and negative output are
used for the feedback network. Because a conventional op amp
does not have a negative output, only its inverting input can be
used for the feedback network. The AD8132 is symmetrical, there-
fore, the feedback network on either side can be used to produce
the same results.
Because +IN is a summing junction, by an analogy to conven-
tional op amps, the gain from V
IN
to OUT is R
F
/R
G
. This holds
true regardless of the voltage on V
OCM
, and since +OUT moves
the same amount in the opposite direction from OUT, the
overall gain is 2(R
F
/R
G
).
V
OCM
still governs V
OUT, cm
, so +OUT must be the only output that
moves when V
OCM
is varied. Because V
OUT, cm
is the average of the
two outputs, +OUT must move twice as far and in the same
direction as V
OCM
to create the proper V
OUT, cm
. Therefore, the
gain from V
OCM
to +OUT must be 2.
With β2 equal to 0 in these circuits, the gain can theoretically
be set to any value from close to 0 to infinity, just as it can with
a conventional op amp in the inverting mode. However, practical
real-world limitations and parasitics limit the range of acceptable
gain to more modest values.
β1 = 0
There is yet another class of circuits where there is no feed-
back from OUT to +IN. This is the case where β1 = 0. The
differential amplifier without a resistor described in the
Differential Amplifier Without Resistors (High Input
Impedance Inverting Amplifier) section meets this condition, but
it was presented only with the condition that β2 = 1. Recall that
this circuit had a gain equal to 2.
If β2 decreases in this circuit from unity, a smaller part of +V
OUT
is fed back to IN and the gain increases (see Figure 68). This
circuit is very similar to a noninverting op amp configuration,
except for the presence of the additional complementary output.
Therefore, the overall gain is twice that of a noninverting op
amp or 2 × (1 + R
F2
/R
G2
) or 2 × (1/β2).
Once again, varying V
OCM
does not affect both outputs in the
same way; therefore, in addition to varying V
OUT, cm
with unity
gain, there is also an effect on V
OUT, dm
by changing V
OCM
.
ESTIMATING THE OUTPUT NOISE VOLTAGE
Similar to the case of a conventional op amp, the differential
output errors (noise and offset voltages) can be estimated by
multiplying the input referred terms, at +IN and IN, by the
circuit noise gain. The noise gain is defined as
+
=
G
F
N
R
R
G
1
To compute the total output referred noise for the circuit of
Figure 64, consideration must be given to the contribution of
resistors, R
F
and R
G
. See Table 11 for estimated output noise
voltage densities at various closed-loop gains.
Table 11. Recommended Resistor Values and Noise
Performance for Specific Gains
Gain
1
2
5
10
R
G
(Ω)
499
499
499
499
R
F
(Ω)
499
1.0 k
2.49 k
4.99 k
Bandwidth
3 dB (MHz)
360
160
65
20
Output
Noise
AD8132
Only
(nV/√Hz)
16
24.1
48.4
88.9
Output
Noise
AD8132
+ R
G
, R
F
(nV/√Hz)
17
26.1
53.3
98.6
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8132ARMZ | 制造商:Analog Devices 功能描述:IC - Differential Amplifier 制造商:Analog Devices 功能描述:IC, DIFF AMP, 350MHZ, 1200V/ uS, MSOP-8 |
| AD8132ARMZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Cost, High Speed Differential Amplifier |
| AD8132ARMZ-REEL | 功能描述:IC AMP DIFF LDIST LP 70MA 8MSOP RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標(biāo)準(zhǔn)包裝:50 系列:- 放大器類型:通用 電路數(shù):2 輸出類型:滿擺幅 轉(zhuǎn)換速率:1.8 V/µs 增益帶寬積:6.5MHz -3db帶寬:4.5MHz 電流 - 輸入偏壓:5nA 電壓 - 輸入偏移:100µV 電流 - 電源:65µA 電流 - 輸出 / 通道:35mA 電壓 - 電源，單路/雙路(±):1.8 V ~ 5.25 V，±0.9 V ~ 2.625 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:10-MSOP 包裝:管件 |
| AD8132ARMZ-REEL1 | 制造商:AD 制造商全稱: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 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 產(chǎn)品培訓(xùn)模塊:Differential Circuit Design Techniques for Communication Applications 標(biāo)準(zhǔn)包裝:1 系列:- 放大器類型:RF/IF 差分 電路數(shù):1 輸出類型:差分 轉(zhuǎn)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(yīng)商設(shè)備封裝:16-LFCSP-VQ 包裝:剪切帶 (CT) 產(chǎn)品目錄頁面:551 (CN2011-ZH PDF) 其它名稱:ADL5561ACPZ-R7CT |
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