參數(shù)資料
型號(hào)： AD8335ACPZ-REEL
廠商： Analog Devices Inc
文件頁(yè)數(shù)： 11/28頁(yè)
文件大?。?/td> 0K
描述： IC AMP VGA QUAD 64LFCSP
產(chǎn)品變化通告： AD8335 Metal Mask Change 12/Jul/2010
標(biāo)準(zhǔn)包裝： 2,500
系列： X-AMP®
類型： 可變?cè)鲆娣糯笃?br>
應(yīng)用： 信號(hào)處理
安裝類型： 表面貼裝
封裝/外殼： 64-VFQFN 裸露焊盤，CSP
供應(yīng)商設(shè)備封裝： 64-LFCSP-VQ（9x9）
包裝： 帶卷 (TR)
配用： AD8335-EVALZ-ND - BOARD EVALUATION FOR AD8335
Data Sheet
AD8335
Rev. B | Page 19 of 28
Output Stage
VGA Noise
Duplicate output stages of the VGA provide an 8 dB (×2.5) gain
switch. The gain switch is intended to optimize the output noise
floor for either a 10-bit or a 12-bit ADC. The VGA gain is 20 dB
(×10) in low gain mode and 28 dB (×25) in high gain mode. The
logic setting of the HLxx pins selects between output amplifiers
including the gain resistors and feedback buffers.
As with all X-AMPs, the output noise of the VGA is constant with
gain. This causes the input referred noise to increase as the gain
is decreased. This characteristic is desirable in receiver applications
where wide dynamic range input signals are compressed with a
fixed ceiling and noise floor into an ADC. The VGA output noise is
approximately 33 nV/√Hz in low gain mode and 2.5 times higher
than this, 83 nV/√Hz, in high gain mode. As the gain increases,
the noise of the preamplifier prevails and, at the maximum VGA
gain, the output noise is approximately 90 nV/√Hz and 225
nV/√Hz for low and high gain modes, respectively.
100 MHz bandwidth is maintained between the amplifiers by
changing the compensation capacitance as the gain switches gain
settings. Power consumption is the same for either level of gain.
In certain applications, power consumption can be reduced by
lowering the supply voltage as much as possible; however, the
output dynamic range is affected by the more limited swing.
The fully differential signal path of the AD8335 restores 6 dB
of dynamic range, and the common-mode level is maintained
automatically at half the supply voltage for maximum signal swing.
The differential signal has the added benefit of suppressing the
even order harmonics.
The output SNR is determined by the noise floor and the largest
signal level, typically limited by the FS of the ADC. Modulation
noise, essentially the noise introduced by the gain control input,
can be troublesome. Normally one tends to look at the main
amplifier signal path for noise, but a VGA is really a multiplier
with the following function:
REF
IN
GAIN
OUT
V
×
=
(5)
The output amplifier is designed to drive a nominal differential
load of 500 Ω or greater; the signal swing can be as large as
5 V p-p differential before clipping occurs. However, that distortion
increases before reaching the clipping level. Distortion is shown
in Figure 25 through Figure 34 for typical values of 1 V p-p or
2 V p-p (full-scale inputs for many ADCs). The output is ac-
coupled to a differential antialias filter driving a differential
ADC. Most modern ADCs have differential inputs and achieve
optimum performance when driven differentially. For more
information, see the Applications Information section.
where VREF (bias) and VGAIN (gain control interface) are both
noise contributors under certain conditions. It is therefore
important that the gain control signals be kept clean, especially
at higher gain control slopes.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD8335ACPZ-REEL7 功能描述:IC AMP VGA QUAD 64LFCSP RoHS:是 類別:集成電路 (IC) >> 線性 - 放大器 - 專用 系列:X-AMP® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:60 系列:- 類型:可變?cè)鲆娣糯笃?應(yīng)用:CATV 安裝類型:表面貼裝 封裝/外殼:20-WQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:20-TQFN-EP（5x5） 包裝:托盤
AD8335EVAL 制造商:Analog Devices 功能描述:EVAL BOARD ((NS))
AD8335-EVAL 制造商:AD 制造商全稱:Analog Devices 功能描述:Quad Low Noise, Low Cost Variable Gain Amplifier
AD8335-EVALZ 功能描述:BOARD EVALUATION FOR AD8335 RoHS:是 類別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - 運(yùn)算放大器 系列:X-AMP® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:-
AD8336 制造商:AD 制造商全稱:Analog Devices 功能描述:General-Purpose, −55 to +125, Wide Bandwidth, DC-Coupled VGA
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