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| 型号： | AD8335-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 11/28页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR AD8335 |
| 产品变化通告： | AD8335 Metal Mask Change 12/Jul/2010 |
| 标准包装： | 1 |
| 系列： | X-AMP® |
| 每 IC 通道数： | 4 - 四 |
| 放大器类型： | 可变增益 |
| 输出类型： | 差分 |
| 转换速率： | 350 V/µs |
| -3db带宽： | 110MHz |
| 工作温度： | -40°C ~ 85°C |
| 电流供应（主 IC）： | 76mA |
| 电压 - 电源，单路/双路(±)： | 4.5 V ~ 5.5 V |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | AD8335 |
| 相关产品： | AD8335ACPZ-ND - IC AMP VGA QUAD 64LFCSP AD8335ACPZ-REEL7-ND - IC AMP VGA QUAD 64LFCSP AD8335ACPZ-REEL-ND - IC AMP VGA QUAD 64LFCSP |
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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
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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| AD8336ACPZ | 制造商:Analog Devices 功能描述:SP AMP VARIABLE GAIN AMP SGL 12V 16LFCSP EP - Bulk |
| AD8336ACPZ-R7 | 功能描述:IC VGA GP SGL-ENDED 16-LFCSP RoHS:是 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:X-AMP® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
| AD8336ACPZ-RL | 功能描述:IC VGA GP SGL-ENDED 16-LFCSP RoHS:是 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:X-AMP® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
| AD8336ACPZ-WP | 功能描述:IC VGA GP SGL-ENDED 16-LFCSP RoHS:是 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:X-AMP® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:60 系列:- 类型:可变增益放大器 应用:CATV 安装类型:表面贴装 封装/外壳:20-WQFN 裸露焊盘 供应商设备封装:20-TQFN-EP（5x5） 包装:托盘 |
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