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參數(shù)資料
| 型號： | AD8370-EVAL |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 運動控制電子 |
| 英文描述： | LF to 750 MHz Digitally Controlled VGA |
| 中文描述： | LF到750兆赫數(shù)字控制VGA |
| 文件頁數(shù)： | 13/28頁 |
| 文件大小： | 1043K |
| 代理商： | AD8370-EVAL |
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AD8370
THEORY OF OPERATION
The AD8370 is a low cost, digitally controlled, fine adjustment
variable gain amplifier that provides both high IP3 and low
noise figure. The AD8370 is fabricated on an ADI proprietary
high performance 25 GHz silicon bipolar process. The –3 dB
bandwidth is approximately 750 MHz throughout the variable
gain range. The typical quiescent current of the AD8370 is
78 mA. A power-down feature reduces the current to less than
4 mA. The input impedance is approximately 200 differential,
and the output impedance is approximately 100 differential to
be compatible with saw filters and matching networks used in
intermediate frequency (IF) radio applications. Because there is
no feedback between the input and output and stages within the
amplifier, the input amplifier is isolated from variations in
output loading and from subsequent impedance changes, and
excellent input to output isolation is realized. Excellent distor-
tion performance and wide bandwidth make the AD8370 a
suitable gain control device for modern differential receiver
designs. The AD8370 differential input and output configuration
is ideally suited to fully differential signal chain circuit designs,
although it can be adapted to single-ended system applications,
if required.
Rev. 0 | Page 13 of 28
BLOCK ARCHITECTURE
The three basic building blocks of the AD8370 are a high/low
gain selectable input preamplifier, a digitally controlled
transconductance (g
m
) block, and a fixed gain output stage.
INHI
INLO
OPHI
OPLO
VCCO
11
OCOM
ICOM
VOCM
PWUP
VCCO
6
OCOM
VCCI
3
ICOM
BIAS CELL
SHIFT REGISTER
AND LATCHES
PRE
AMP
TRANSCONDUCTANCE
OUTPUT
AMP
1
16
4
14
13
12
5
9
8
2
10
7
15
DATA CLCK LTCH
AD8370
0
Figure 35. Functional Block Diagram
PREAMPLIFIER
There are two selectable input preamplifiers. Selection is made
by the most significant bit (MSB) of the serial gain control data-
word. In the high gain mode, the overall device gain is 7.1 Volts/
Volt (17 dB) above the low gain setting. The two preamplifiers
give the AD8370 the ability to accommodate a wide range of
input amplitudes. The overlap between the two gain ranges
allows the user some flexibility based on noise and distortion
demands. See the Choosing between Gain Ranges section for
more information.
The input impedance is approximately 200 differential,
regardless of which preamplifier is selected. Note that the input
impedance is formed by using active circuit elements and is not
set by passive components. See Figure 36 for a simplified
schematic of the input interface.
1mA
1mA
VCC/2
2k
INHI/INLO
0
Figure 36. INHI/INLO Simplified Schematic
TRANSCONDUCTANCE STAGE
The digitally controlled g
m
section has 42 dB of controllable
gain and makes gain the adjustments within each gain range.
The step size resolution ranges from a fine ~ 0.07 dB up to a
coarse 6 dB per bit, depending on the gain code. As shown in
Figure 37, of the 42 dB total range, 28 dB has resolution of
better than 2 dB, and 22 dB has resolution of better than 1 dB.
The curves in Figure 37 show typical input levels that can be
applied to this amplifier at different gain settings. The maxi-
mum input was determined by finding the 1 dB compression or
expansion point of the V
OUT
/V
SOURCE
gain. Note that this is not
V
OUT
/V
IN
. In this way, the change in the input impedance of the
device is also taken into account.
0
0.4
0.8
1.2
1.6
2.0
V
O
2.4
2.8
3.2
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
V
SOURCE
[V peak] (V)
0
HIGH GAIN
0.1dB GAIN
–5dB GAIN
–8dB GAIN
12dB
GAIN
6dB
GAIN
<2dB
RES
<2dB
RES
<1dB
RES
<1dB
RES
<0.5dB
RESOLUTION
<0.5dB
RES
–11dB GAIN
–25dB GAIN
17dB
GAIN
34dB
GAIN
LOW GAIN
Figure 37. Gain Resolution and Nominal Input and
Output Range over the Gain Range
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AD8370-EVALZ | 制造商:Analog Devices 功能描述:- Bulk |
| AD8372 | 制造商:AD 制造商全稱:Analog Devices 功能描述:41 dB Range, 1 dB Step Size, Programmable Dual VGA |
| AD8372ACPZ-R7 | 功能描述:IC AMP VGA DIFF DUAL LN 32LFCSP RoHS:是 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):4 輸出類型:- 轉換速率:0.6 V/µs 增益帶寬積:1MHz -3db帶寬:- 電流 - 輸入偏壓:45nA 電壓 - 輸入偏移:2000µV 電流 - 電源:1.4mA 電流 - 輸出 / 通道:40mA 電壓 - 電源，單路/雙路(±):3 V ~ 32 V，±1.5 V ~ 16 V 工作溫度:0°C ~ 70°C 安裝類型:表面貼裝 封裝/外殼:14-TSSOP（0.173"，4.40mm 寬） 供應商設備封裝:14-TSSOP 包裝:帶卷 (TR) 其它名稱:LM324ADTBR2G-NDLM324ADTBR2GOSTR |
| AD8372ACPZ-R71 | 制造商:AD 制造商全稱:Analog Devices 功能描述:41 dB Range, 1 dB Step Size, Programmable Dual VGA |
| AD8372ACPZ-WP | 制造商:Analog Devices 功能描述: 制造商:Rochester Electronics LLC 功能描述: |
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