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參數(shù)資料
| 型號： | AD8045 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | 3 nV/Hz Ultralow Distortion, High Speed Op Amp |
| 中文描述： | 3內(nèi)華達州/ Hz的超低失真，高速運算放大器 |
| 文件頁數(shù)： | 20/24頁 |
| 文件大小： | 474K |
| 代理商： | AD8045 |
AD8045
Rev. A | Page 20 of 24
0
FREQUENCY (MHz)
0
5
10
15
20
25
30
D
0
–20
–40
–60
–80
–100
–120
A
= –1dBFS
SNR = 69.9dBc
SFDR = 65.3dBc
Figure 69. Single-Tone FFT, F
IN
= 50 MHz, Sample Rate = 65 MSPS
Shown in the First Nyquist Zone
90 MHZ ACTIVE LOW-PASS FILTER (LPF)
Active filters are used in many applications such as antialiasing
filters and high frequency communication IF strips.
With a 400 MHz gain bandwidth product and high slew rate,
the AD8045 is an ideal candidate for active filters. Figure 70
shows the frequency response of the 90 MHz LPF. In addition to
the bandwidth requirements, the slew rate must be capable of
supporting the full power bandwidth of the filter. In this case, a
90 MHz bandwidth with a 2 V p-p output swing requires at least
1200 V/μs. This performance is achievable only at 90 MHz
because of the AD8045’s wide bandwidth and high slew rate.
The circuit shown in Figure 73 is a 90 MHz, 4-pole, Sallen-Key,
LPF. The filter comprises two identical cascaded Sallen-Key LPF
sections, each with a fixed gain of G = +2. The net gain of the
filter is equal to G = +4 or 12 dB. The actual gain shown in
Figure 70 is only 6 dB. This is due to the output voltage being
divided in half by the series matching termination resistor, R
T
,
and the load resistor.
Setting the resistors and capacitors equal to each other greatly
simplifies the design equations for the Sallen-Key filter. The
corner frequency, or 3 dB frequency, can be described by the
equation
RC
f
c
2π
1
=
The quality factor, or
Q,
is shown in the equation
K
Q
=
3
1
The gain, or
K,
of the circuits are
1
1,
+
=
+
=
R7
R8
K
Stage
Second
R4
R3
K
Stage
First
Resistor values are kept low for minimal noise contribution,
offset voltage, and optimal frequency response. Due to the low
capacitance values used in the filter circuit, the PCB layout and
minimization of parasitics is critical. A few picofarads can detune
the filters corner frequency, f
c
. The capacitor values shown in
Figure 73 actually incorporate some stray PCB capacitance.
Capacitor selection is critical for optimal filter performance.
Capacitors with low temperature coefficients, such as NPO
ceramic capacitors and silver mica, are good choices for filter
elements.
0
FREQUENCY (MHz)
0.1
1
10
100
1000
G
–40
–30
–20
0
–10
10
–50
–60
–70
–80
–90
20
Figure 70. 90 MHz Low-Pass Filter Response
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AD8045ACP-EBZ | 功能描述:BOARD EVAL FOR AD8045ACP RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - 運算放大器 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:1 系列:- |
| ad8045acp-r2 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
| AD8045ACP-REEL | 制造商:AD 制造商全稱:Analog Devices 功能描述:3 nV/Hz Ultralow Distortion, High Speed Op Amp |
| AD8045ACP-REEL7 | 制造商:Analog Devices 功能描述:OP Amp Single Volt Fdbk |
| AD8045ACPZ-R2 | 制造商:Analog Devices 功能描述:OP Amp Single Volt Fdbk 制造商:Analog Devices 功能描述:OP AMP SGL VOLT FDBK 6V/12V 8LFCSP EP - Tape and Reel 制造商:Analog Devices 功能描述:AMP VOLT FEEDBACK 8045 LFCSP-8 制造商:Analog Devices 功能描述:AMP, VOLT FEEDBACK, 8045, LFCSP-8 |
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