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| 型號： | AD8390ACP-EVAL |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 運動控制電子 |
| 英文描述： | Low Power, High Output Current Differential Amplifier |
| 中文描述： | 低功耗，高輸出電流差動放大器 |
| 文件頁數(shù)： | 11/16頁 |
| 文件大小： | 531K |
| 代理商： | AD8390ACP-EVAL |
AD8390
Rev. C | Page 11 of 16
0
P
P
R
M
R
L
V
OUT,DM
–
+
–OUT
+OUT
R
M
R3
R2
R1
R1
R3
0.1
μ
F
I
A
R
ADJ
R2
1:N
10
μ
F
0.1
μ
F
V
CC
+IN
V
OCM
–IN
10
μ
F
0.1
μ
F
0.1
μ
F
V
EE
Figure 24. ADSL/ADSL2+ Application Circuit
Referring to Figure 24, the following describes how to calculate
the resistor values necessary to obtain the desired input imped-
ance, gain, and output impedance.
The differential input impedance to the circuit is simply 2
R1
.
As such,
R1
is chosen by the designer to yield the desired input
impedance.
When synthesizing the output impedance, a factor
k
is
introduced
,
which is used to express the ratio of the negative
feedback resistor to the positive feedback resistor by
R2
R3
k
=
1
(5)
Along with the turns ratio
N
,
k
is also used to define the value of
the back termination resistors R
M
. Commonly used values for
k
are 0.1 to 0.25. A
k
value of 0.1 would result in back termination
resistors that are only 1/10 as large as those in the simplest case
described above. Lower values of
k
result in greater amounts of
positive feedback. Therefore, values much lower than 0.1 can
lead to instability and are generally not recommended.
2
2
N
×
R
k
R
L
M
×
=
(6)
This factor (
k
), along with
R1
,
R
M
, and the desired gain (
A
V
), is
then used to calculate the necessary values for
R3
and
R2
.
(
)
(7)
M
M
V
V
V
R
k
R
k
R1
A
R1
A
k
R1
A
R3
×
+
×
×
×
×
+
×
×
=
2
The usually small value for
R
M
allows a simplified approximation
for
R3
.
V
A
k
R1
R3
×
×
×
2
(8)
k
R3
R2
=
1
(9)
Once
R
M
,
R3
, and
R2
are computed, the closest 1% resistors can
be chosen and the gain rechecked with the following equation:
(
)
R1
×
R3
R2
R2
k
R
R3
R2
A
M
V
+
×
+
×
=
(10)
Table 6 shows a comparison of the results using the exact values,
the simplified approximation, and the closest 1% resistor values.
In this example,
R1
,
A
V
, and
k
were chosen to be 1.0 k, 10 k,
and 0.1 k, respectively.
It should be noted that decreasing the value of the back termi-
nation resistors attenuates the receive signal by approximately
1/k. However, advances in low noise receive amplifiers permit
k values as small as 0.1 to be commonly used.
The line impedance, turns ratio, and k factor specify the output
voltage and current requirements from the AD8390. To accom-
modate higher crest factors or lower supply rails, the turns ratio,
N, may have to be increased. Since higher turns ratios and smaller
k factors both attenuate the receive signal, a large increase in N
may require an increase in k to maintain the desired noise
performance. Any particular design process requires that these
trade-offs be visited.
Table 6. Resistor Selection
Component
R1 ()
R2 ()
R3 ()
R
M
()
Actual A
V
Actual k (Eq. 5)
Exact
Values
1000
2246.95
2022.25
5
10.000
0.1
Approximate
Calculation
1000
2222.22
2000
5
9.889
0.1
Standard 1%
Resistor
Values
1000
2210
2000
4.99
10.138
0.095
MULTITONE POWER RATIO (MTPR)
Multitone power ratio is a commonly used figure of merit that
xDSL designers use to help describe system performance.
MTPR is the measured delta between the peak of a filled
frequency bin and the harmonic products that appear in an
intentionally empty frequency bin. Figure 25 illustrates this
principle. The plots in Figure 10 and Figure 13 show MTPR
performance in various power modes. All data were taken with
a circuit with a k factor of 0.1, a 1:1 turns ratio transformer, and
a waveform with a 5.4 peak-to-average ratio, also known as the
crest factor (CF).
0
–70dBc
10dB/DIV
CENTER 431.25kHz
SPAN 10kHz
1kHz/DIV
Figure 25. MTPR Measurement
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| AD8390ARC-EVAL | Circular Connector; MIL SPEC:MIL-DTL-38999 Series III; Body Material:Metal; Series:D38999 Series III; No. of Contacts:10; Connector Shell Size:13; Connecting Termination:Crimp; Circular Shell Style:Straight Plug; Body Style:Straight RoHS Compliant: No |
相關(guān)代理商/技術(shù)參數(shù) |
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| AD8390ACP-R2 | 功能描述:IC AMP DIFF LP LDIST 16LFCSP RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:2,500 系列:- 放大器類型:通用 電路數(shù):1 輸出類型:滿擺幅 轉(zhuǎn)換速率:0.11 V/µs 增益帶寬積:350kHz -3db帶寬:- 電流 - 輸入偏壓:4nA 電壓 - 輸入偏移:20µV 電流 - 電源:260µA 電流 - 輸出 / 通道:20mA 電壓 - 電源，單路/雙路(±):2.7 V ~ 36 V，±1.35 V ~ 18 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:8-SO 包裝:帶卷 (TR) |
| AD8390ACP-REEL | 制造商:Analog Devices 功能描述:SP Amp DIFF AMP Single ±12V/24V 16-Pin LFCSP EP T/R |
| AD8390ACP-REEL7 | 制造商:Analog Devices 功能描述:SP Amp DIFF AMP Single 制造商:Rochester Electronics LLC 功能描述:ADSL LINE DRIVER - Tape and Reel 制造商:Analog Devices 功能描述:IC AMP LOW POWER |
| AD8390ACPZ-R2 | 制造商:Analog Devices 功能描述:SP Amp DIFF AMP Single ±12V/24V 16-Pin LFCSP EP T/R 制造商:Analog Devices 功能描述:SP AMP DIFF AMP SGL 12V/24V 16LFCSP EP - Tape and Reel |
| AD8390ACPZ-REEL | 制造商:Analog Devices 功能描述:SP Amp DIFF AMP Single ±12V/24V 16-Pin LFCSP EP T/R 制造商:Analog Devices 功能描述:SP AMP DIFF AMP SGL 12V/24V 16LFCSP EP - Tape and Reel |
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