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參數(shù)資料
| 型號(hào)： | AD8001 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Current Feedback Amplifier(800MHz,50mW電流反饋放大器) |
| 中文描述： | 電流反饋放大器（800MHz的，50mW的電流反饋放大器） |
| 文件頁(yè)數(shù)： | 10/16頁(yè) |
| 文件大?。?/td> | 372K |
| 代理商： | AD8001 |
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AD8001
REV. B
–10–
V
O
V
IN
=
G
×
T
Z
(
S
)
T
Z
(
S
)
+
G
×
R
IN
+
R
1
G
=
1
+
R
1
R
2
R
IN
=
1/
g
M
≈
50
T HE ORY OF OPE RAT ION
A very simple analysis can put the operation of the AD8001, a
current feedback amplifier, in familiar terms. Being a current
feedback amplifier, the AD8001’s open-loop behavior is ex-
pressed as transimpedance,
V
O
/
I
–IN
, or T
Z
. T he open loop
transimpedance behaves just as the open loop voltage gain of a
voltage feedback amplifier, that is, it has a large dc value and
decreases at roughly 6 dB/octave in frequency.
Since the R
IN
is proportional to 1/g
M
, the equivalent voltage
gain is just T
Z
×
g
M
, where the g
M
in question is the trans-
conductance of the input stage. T his results in a low open loop
input impedance at the inverting input, a now familiar result.
Using this amplifier as a follower with gain, Figure 40, basic
analysis yields the following result.
Recognizing that G
×
R
IN
<< R
1
for low gains, it can be seen to
the first order that bandwidth for this amplifier is independent
of gain (G). T his simple analysis in conjunction with Figure 41
in fact can predict the behavior of the AD8001 over a wide
range of conditions.
V
OUT
R1
R2
R
IN
V
IN
Figure 40.
Considering that additional poles contribute excess phase at
high frequencies there is a minimum feedback resistance below
which peaking or oscillation may result. T his fact is used to de-
termine the optimum feedback resistance, R
F
. In practice para-
sitic capacitance at Pin 2 will also add phase in the feedback
loop, so picking an optimum value for R
F
can be difficult. Fig-
ure 42 illustrates this problem. Here the fine scale (0.1 dB/div)
flatness is plotted vs. feedback resistance. T hese plots were
taken using an evaluation card which is available to customers
so that these results may readily duplicated (see Evaluation
Board section).
Achieving and maintaining gain flatness of better than 0.1 dB at
frequencies above 10 MHz requires careful consideration of sev-
eral issues.
FREQUENCY – Hz
T
Z
1M
10
100k
1M
1G
100M
10M
100
100k
10k
1k
Figure 41. Transimpedance vs. Frequency
O
0.1
0
–0.9
1M
10M
100M
–0.1
–0.2
–0.3
–0.4
–0.5
FREQUENCY – Hz
–0.6
–0.7
–0.8
R
F
=
649
R
F
= 698
R
F
= 750
G = +2
Figure 42. 0.1 dB Flatness vs. Frequency
Choice of Feedback and Gain Resistors
Because of the above mentioned relationship between the band-
width and the feedback resistor, the fine scale gain flatness will,
to some extent, vary with feedback resistance. It, therefore, is
recommended that once optimum resistor values have been
determined, 1% tolerance values should be used if it is desired
to maintain flatness over a wide range of production lots. In ad-
dition, resistors of different construction have different associ-
ated parasitic capacitance and inductance. Surface mount
resistors were used for the bulk of the characterization for this
data sheet. It is not recommended that leaded components be
used with the AD8001.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8001_03 | 制造商:AD 制造商全稱:Analog Devices 功能描述:800 MHz, 50 mW Current Feedback Amplifier |
| AD800-10-TO5I | 功能描述:光電二極管 800um active area APD chip w/ IR RoHS:否 制造商:Vishay Semiconductors 產(chǎn)品:Photodiodes 反向電壓:10 V 最大暗電流:30 nA 峰值波長(zhǎng):565 nm 上升時(shí)間:3.1 us 下降時(shí)間:3 us 半強(qiáng)度角度:50 deg 封裝 / 箱體:TO-5 |
| AD800-11-TO52S1.3 | 功能描述:光電二極管 800um active area APD chip w/ Blue RoHS:否 制造商:Vishay Semiconductors 產(chǎn)品:Photodiodes 反向電壓:10 V 最大暗電流:30 nA 峰值波長(zhǎng):565 nm 上升時(shí)間:3.1 us 下降時(shí)間:3 us 半強(qiáng)度角度:50 deg 封裝 / 箱體:TO-5 |
| AD80013AJSTRL | 制造商:Analog Devices 功能描述: |
| AD80013JST | 制造商:Analog Devices 功能描述: |
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