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參數(shù)資料
| 型號(hào)： | AD8337-EVALZ-SS |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 10/32頁 |
| 文件大?。?/td> | 0K |
| 描述： | BOARD EVALUATION FOR AD8337 SS |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 系列： | X-AMP® |
| 每 IC 通道數(shù)： | 1 - 單 |
| 放大器類型： | 電壓反饋 |
| 輸出類型： | 單端 |
| 轉(zhuǎn)換速率： | 625 V/µs |
| -3db帶寬： | 280MHz |
| 工作溫度： | -40°C ~ 85°C |
| 電流供應(yīng)（主 IC）： | 18.5mA |
| 電壓 - 電源，單路/雙路(±)： | 5 V ~ 10 V |
| 板類型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | AD8337 |
| 相關(guān)產(chǎn)品： | AD8337BCPZ-REEL7-ND - IC AMP VGA LOW NOISE 8-LFCSP AD8337BCPZ-REEL-ND - IC AMP VGA LOW NOISE 8-LFCSP AD8337BCPZ-WP-ND - IC AMP VGA DC-COUPLED GP 8-LFCSP AD8337BCPZ-R2DKR-ND - IC AMP VGA LOW NOISE 8-LFCSP AD8337BCPZ-R2CT-ND - IC AMP VGA LOW NOISE 8-LFCSP AD8337BCPZ-R2TR-ND - IC AMP VGA LOW NOISE 8-LFCSP |
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AD8337
Rev. C | Page 18 of
32
THEORY OF OPERATION
VOUT
GAIN
RG
18dB
(8x)
2
1
6
PRAO
VNEG
VCOM
+
–
7
749
107
PrA
6dB
GAIN
INTERFACE
BIAS
+
–
8
VPOS
INPP
INPN
5
3
4
INTERPOLATOR
ATTENUATOR
–24dB TO 0dB
+
–
RFB1 = RFB2 = 100
05
57
5-
0
65
RFB2
RFB1
Figure 65. Circuit Block Diagram
OVERVIEW
The AD8337 is a low noise, single-ended, linear-in-dB, general-
purpose variable gain amplifier (VGA) usable at frequencies up
to 100 MHz. It is fabricated using a proprietary Analog Devices
dielectrically isolated, complementary bipolar process. The
bandwidth is dc to 280 MHz and features low dc offset voltage
and an ideal nominal gain range of 0 dB to 24 dB. Requiring
about 15.5 mA, the power consumption is only 78 mW from
either a single +5 V or a dual ±2.5 V supply. Figure 65 is the
circuit block diagram of the AD8337.
PREAMPLIFIER
An uncommitted current-feedback op amp included in the
AD8337 can be used as a preamplifier to buffer the ladder
network attenuator of the X-AMP. As with any op amp, the gain
is established using external resistors, and the preamplifier is
specified with a noninverting gain of 6 dB (2×) and gain resistor
values of 100 Ω. The preamplifier gain can be increased using
larger values of RFB2, trading off bandwidth and offset voltage.
The value of RFB2 is to be ≥100 Ω because the value and an
internal compensation capacitor determine the 3 dB bandwidth,
and smaller values can compromise preamplifier stability.
Because the AD8337 is dc-coupled, larger preamp gains increase
the offset voltage. The offset voltage can be compensated by
connecting a resistor between the INPN input and the supply
voltage. If the offset is negative, the resistor value connects to
the negative supply. For ease of adjustment, a trimmer network
can be used.
For larger gains, the overall noise is reduced if a low value of
RFB1 is selected. For values of RFB1 = 20 Ω and RFB2 = 301 Ω, the
preamp gain is 16× (24.1 dB), and the input-referred noise is
approximately 1.5 nV/√Hz. For this value of gain, the overall
gain range increases by 18 dB; therefore, the gain range is 18 dB
to 42 dB.
VGA
This X-AMP, with its linear-in-dB gain characteristic
architecture, yields the optimum dynamic range for receiver
applications. Referring to Figure 65, the signal path consists of
a 24 dB variable attenuator followed by a fixed gain amplifier of
18 dB, for a total VGA gain range of 6 dB to +18 dB. With the
preamplifier configured for a gain of 6 dB, the composite gain
range is 0 dB to 24 dB.
The VGA plus preamp, with 6 dB of gain, implements the
following exact gain law:
(dB)
V
dB
19.7
(dB)
ICPT
GAIN
V
Gain
+
×
=
where the nominal intercept (ICPT) = 12.65 dB.
The ICPT increases as the gain of the preamp is increased. For
example, if the gain of the preamp is increased by 6 dB, ICPT
increases to 18.65 dB. Although the previous equation shows
the exact gain law as based on statistical data, a quick estimation
of signal levels can be made using the default slope of 20 dB/V
for a particular gain setting. For example, the change in gain for
a VGAIN change of 0.3 V is 6 dB using a slope of 20 dB/V and
5.91 dB using the exact slope of 19.6 dB/V. This is a difference
of only 0.09 dB.
GAIN CONTROL
The gain control interface provides a high impedance input and
is referenced to the VCOM pin (in a single-supply application to
midsupply at [VPOS + VNEG]/2 for optimum swing). When
dual supplies are used, VCOM is connected to ground. The voltage
on the VCOM pin determines the midpoint of the gain range. For
a ground referenced design, the VGAIN range is from 0.7 V to
+0.7 V with the most linear-in-dB section of the gain control
between 0.6 V and +0.6 V. In the center 80% of the VGAIN
range, the gain error is typically less than ±0.2 dB. The gain
control voltage can be increased or decreased to the positive or
negative rails without gain foldover.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8338 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Power, 18 MHz Variable Gain Amplifier |
| AD8338ACPZ-R7 | 功能描述:特殊用途放大器 Ultra Low Pwr 18MHz SGL CH VGA RoHS:否 制造商:Analog Devices 通道數(shù)量:Single 共模抑制比（最小值）: 輸入補(bǔ)償電壓: 工作電源電壓:5 V 電源電流:133 mA 最大功率耗散:900 mW 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-28 封裝:Reel |
| AD8338ACPZ-RL | 制造商:Analog Devices 功能描述:AMPLIFIER - SPECIAL PURPOSE |
| AD8338-EVALZ | 功能描述:AD8338 1 - Single Channels per IC Variable Gain Amplifier Evaluation Board 制造商:analog devices inc. 系列:- 零件狀態(tài):有效 每 IC 通道數(shù):1 - 單 放大器類型:可變?cè)鲆?輸出類型:差分 壓擺率:50 V/μs -3db 帶寬:18MHz 電流 - 輸出/通道:- 工作溫度:-40°C ~ 85°C 電流 - 電源（主 IC）:- 電壓 - 電源，單/雙（±）:3.5 V ~ 5 V 板類型:完全填充 所含物品:板 使用的 IC/零件:AD8338 標(biāo)準(zhǔn)包裝:1 |
| AD8339 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Quad I/Q Demodulator And Phase Shifter |
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