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| 型號： | AD8366ACPZ-R7 |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 7/28頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC DUAL AMP VGA 32LFCSP |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 放大器類型： | 可變增益 |
| 電路數(shù)： | 2 |
| 輸出類型： | 差分 |
| 轉(zhuǎn)換速率： | 1100 V/µs |
| -3db帶寬： | 600MHz |
| 電流 - 電源： | 180mA |
| 電壓 - 電源，單路/雙路(±)： | 4.75 V ~ 5.25 V |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 32-VFQFN 裸露焊盤，CSP |
| 供應(yīng)商設(shè)備封裝： | 32-LFCSP-VQ |
| 包裝： | 標(biāo)準(zhǔn)包裝 |
| 其它名稱： | AD8366ACPZ-R7DKR |
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AD8366
Rev. A | Page 15 of 28
CIRCUIT DESCRIPTION
The AD8366 is a dual, differential, digitally controlled VGA
with 600 MHz of 3 dB bandwidth and a gain range of 4.5 dB to
20.25 dB adjustable in 0.25 dB steps. Using a proprietary variable
gain architecture, the AD8366 is able to achieve excellent linearity
(45 dBm) and noise performance (11.7 nV/√Hz) at 10 MHz at
minimum gain. Intended for use in direct conversion systems, the
part also includes dc offset correction that can be disabled easily
by grounding either OFSA or OFSB. In addition, the part offers
an adjustable output common-mode range of 1.6 V to 3 V.
The main signal path is shown in Figure 46. It consists of an
input transconductance, a variable-gain cell, and an output
transimpedance amplifier.
100
12.5
VARIABLE
CURRENT-GAIN
STAGE
OUTPUT
BUFFER
Z
AI
VIRTUAL
GROUND
VIRTUAL
GROUND
INP
INM
OUTP
OUTM
0
75
84
-0
71
Figure 46. Main Signal Path
The input transconductance provides a broadband 200 Ω
differential termination and converts the input voltage to a
current. This current is fed into the variable current-gain cell.
The output of this cell goes into the transimpedance stage, which
generates the output voltage. The transimpedance is fixed at 500 Ω,
with a roughly 25 Ω differential output impedance.
INPUTS
The inputs to the digitally-controlled VGAs in the AD8366 are
differential and can be either ac- or dc-coupled. The AD8366
synthesizes a 200 Ω (differential) input impedance, with a return
loss (re: 200 Ω) of better than 10 dB to 200 MHz. The nominal
common-mode input voltage to the part is VPOS/2, but the AD8366
can be dc-coupled to parts with lower common modes if these
parts can sink current. The amount of current sinking required
depends on the input common-mode level and is given by
ISINK (per leg) = (VPOS/2 VICM)/100
The input common-mode range is 1.5 V to VPOS/2.
OUTPUTS
The outputs of the digitally-controlled VGAs are differential and
can be either ac- or dc-coupled. The AD8366 synthesizes a 25 Ω
differential output impedance, with a return loss (re: 25 Ω) of
better than 10 dB to 120 MHz. The nominal common-mode
output voltage is VPOS/2; however, it can be lowered or raised by
driving the VCMA or VCMB pins.
OUTPUT DIFFERENTIAL OFFSET CORRECTION
To prevent significant levels of offset from appearing at the
outputs of the AD8366, each digitally controlled VGA has a
differential offset correction loop, as shown in Figure 47. This
loop senses any differential offset at the output and corrects for
it by injecting an opposing current at the input differential ground.
The loop is able to correct for input dc offsets of up to ±20 mV.
Because the loop automatically nulls out any dc or low frequency
offset, the effect of the loop is to introduce a high-pass corner into
the transfer function of the digitally controlled VGA. The
location of this high-pass corner depends on both the gain
setting and the value of the capacitor connected to the OFSx pin
(OFSA for DVGA A and OFSB for DVGA B) and is given by
()
10
2π
4000
1.037
4300
kHz
,
3
+
=
OFS
GC
HP
dB
C
f
where:
GC is the gain code (a value from 0 to 63).
COFS is the value of the capacitance connected to OFSA or OFSB,
in picofarads (pF).
The offset correction loop can be disabled by grounding either
OFSA or OFSB.
gm1
gm2
INP
INM
OFFSET
COMPENSATION
LOOP
VARIABLE-GAIN
STAGE
OUTPUT
BUFFER
Z
AI
OUTP
OUTM
COFS
07
58
4-
0
73
Figure 47. Differential Offset Correction Loop
OUTPUT COMMON-MODE CONTROL
To interface to ADCs that require different input common-mode
voltages, the AD8366 has an adjustable output common-mode
level. The output common-mode level is normally set to VPOS/2;
however, it can be changed between 1.6 V and 3 V by driving
the VCMA pin or the VCMB pin. The input equivalent circuit
for the VCMA pin is shown in Figure 48; the VCMB pin has the
same input equivalent circuit.
4k
500
VPOS/2
VCMA
07
58
4-
07
2
Figure 48. Input Equivalent Circuit for VCMA
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8366-EVALZ | 制造商:AD 制造商全稱:Analog Devices 功能描述:DC to 500 MHz, Dual Digital Gain Trim Amplifier |
| AD8367 | 制造商:AD 制造商全稱:Analog Devices 功能描述:500 MHz, Linear-in-dB VGA with AGC Detector |
| AD8367_05 | 制造商:AD 制造商全稱:Analog Devices 功能描述:500 MHz, Linear-in-dB VGA with AGC Detector |
| AD8367ARU | 功能描述:IC AMP VGA 14TSSOP RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:X-AMP® 標(biāo)準(zhǔn)包裝:2,500 系列:Excalibur™ 放大器類型:J-FET 電路數(shù):1 輸出類型:- 轉(zhuǎn)換速率:45 V/µs 增益帶寬積:10MHz -3db帶寬:- 電流 - 輸入偏壓:20pA 電壓 - 輸入偏移:490µV 電流 - 電源:1.7mA 電流 - 輸出 / 通道:48mA 電壓 - 電源，單路/雙路(±):4.5 V ~ 38 V，±2.25 V ~ 19 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-SOIC 包裝:帶卷 (TR) |
| AD8367ARU-REEL | 制造商:Analog Devices 功能描述: |
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