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| 型号： | AD8260ACPZ-WP |
| 厂商： | Analog Devices Inc |
| 文件页数： | 15/32页 |
| 文件大小： | 0K |
| 描述： | IC AMP VGA DIFF LN 310MA 32LFCSP |
| 标准包装： | 36 |
| 放大器类型： | 可变增益 |
| 电路数： | 1 |
| 输出类型： | 差分 |
| 转换速率： | 730 V/µs |
| -3db带宽： | 195MHz |
| 电流 - 输入偏压： | 200nA |
| 电流 - 电源： | 28.3mA |
| 电流 - 输出 / 通道： | 310mA |
| 电压 - 电源，单路/双路(±)： | 3.3 V ~ 10 V，±3.3 V ~ 5 V |
| 工作温度： | -40°C ~ 105°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 32-VFQFN 裸露焊盘，CSP |
| 供应商设备封装： | 32-LFCSP-VQ |
| 包装： | 托盘 - 晶粒 |
| 配用： | AD8260-EVALZ-ND - BOARD EVAL FOR AD8260 |
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AD8260
Rev. A | Page 22 of 32
PRECAUTIONS TO BE OBSERVED DURING HALF-
DUPLEX OPERATION
During receive, when the high current driver-amplifier is
disabled, its gain setting resistors provide a signal path from
input to output. To prevent inadvertent DAC signals from being
transmitted while receiving via the preamplifier and DGA, the
DAC in Figure 64 must have no output signal.
During transmit, the preamplifier and VGA should be disabled
through any of the nongain-setting codes (see Table 4).
VMID BUFFER
The VMID buffer is a dc bias source that generates the voltage
on Pin 1 and Pin 19, VMDO. Node VMDO cannot accommodate
large dynamic currents and requires excellent ac decoupling to
ground. A high quality 0.1μF capacitor located as close as
possible to Pin 1 and Pin 19 (see Figure 64) is normally sufficient
to decouple the high values of current from Node VMDO.
When operating with dual power supplies, the buffer is disabled
by connecting Pin VMDI, Pin VOCM, and Pin VMDO to ground.
Because the logic decoder in the DGA (GNSx inputs) requires
3.3 V of headroom, the positive supply rails must be 3.3 V or
greater whether single-ended or dual. If a dual supply is used,
the negative rails are the same magnitude (opposite polarity)
as the positive, that is, 3.3 V when VPOS, VPSB, and VPSR
are +3.3 V.
PREAMPLIFIER
The AD8260 includes an uncommitted current feedback op
amp to buffer the resistive attenuator of the DGA. External
resistors are used to adjust the gain. The preamplifier is
characterized with a noninverting gain of 6 dB (2×) and both
gain resistor values of 100 . The preamplifier gain can be
increased using different gain ratios of RFB1 and RFB2, trading off
bandwidth and offset voltage. The sum of the values of RFB1 and
RFB2 should be ≥200 to maintain low distortion. RFB2 should
be ≥100 because it and an internal compensation capacitor
determine the 3 dB bandwidth of the amplifier. Smaller
resistor values may compromise preamplifier stability.
Because the AD8260 is internally dc-coupled, larger preamplifier
gains increase its offset voltage. The circuit contains an internal
bias resistor and some offset compensation; however, if a lower
value of offset voltage is required, it can be compensated by
connecting a resistor between the FDBK pin and the supply
voltage. If the offset is negative, the resistor value connects to
the negative supply; otherwise, it connects to the positive supply.
For larger gains, the overall noise is reduced if a low value of
RFB1 is selected. For values of RFB1 = 20 and RFB2 = 301 , the
preamplifier gain is 16× (24.1 dB) and the input-referred noise
is about 1.5 nV/√Hz. For this value of gain, the overall gain range
increases by 18 dB so that the absolute gain range is 12 dB to 42 dB.
PREAMPLIFIER NOISE
The total input-referred voltage and current noise of the positive
input of the preamplifier is about 2.4 nV/√Hz and 5 pA/√Hz,
respectively. The DGA output referred noise is about 25 nV/√Hz
at low gains and 39 nV/√Hz at the highest gain. The 25 nV/√Hz
divided by the DGA fixed gain of 8× results in 3.12 nV/√Hz
referred to the DGA input. Note that this value includes the
noise of the DGA gain setting resistors as well. If this voltage is
divided by the preamplifier gain of 2×, the DGA noise referred
all the way to the preamplifier input is about 1.56 nV/√Hz. From
this, it can be determined that the preamplifier, including the
100 gain setting resistors, contributes about 1.8 nV/√Hz. The
two 100 resistors each contribute 1.29 nV/√Hz at the output
of the preamplifier and 0.9 nV/√Hz referred to the input. With
the gain resistor noise subtracted, the preamplifier noise alone
is about 1.6 nV/√Hz.
Equation 1 shows the calculation that determines the output-
referred noise at maximum gain (24 dB or 16×).
(
)
2
,
2
,
2
1
2
,
2
,
2
,
2
,
)
(
)
(
)
(
)
(
)
(
VGA
n
VGA
RFB2
n
VGA
FB
RFB1
n
S
PrA
n
t
PrA
n
t
RS
n
out
n
A
e
A
e
A
R
e
R
i
A
e
A
e
×
+
×
+
×
+
×
+
×
+
×
=
(1)
where:
At is the total gain from preamplifier input to the VGA output.
en,RS is the noise of the source resistance.
en,PrA is the input-referred voltage noise of the preamplifier.
in,PrA is the current noise of the preamplifier at the PRAI pin.
RS is the source resistance.
AVGA is the VGA gain.
en,RFB1 is the voltage noise of RFB1.
en,RFB2 is the voltage noise of RFB2.
en,VGA is the input-referred voltage noise of DGA (low gain output-referred noise divided by a fixed gain of 8×).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8260-EVALZ | 功能描述:BOARD EVAL FOR AD8260 RoHS:是 类别:编程器，开发系统 >> 评估板 - 运算放大器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- |
| AD8264 | 制造商:AD 制造商全称:Analog Devices 功能描述:Quad, 235 MHz, DC-Coupled VGA and Differential Output Amplifier |
| AD8264ACPZ | 功能描述:IC AMP VGA DIFF QUAD LN 40LFCSP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:1 系列:- 放大器类型:通用 电路数:4 输出类型:满摆幅 转换速率:0.028 V/µs 增益带宽积:105kHz -3db带宽:- 电流 - 输入偏压:3nA 电压 - 输入偏移:100µV 电流 - 电源:3.3µA 电流 - 输出 / 通道:12mA 电压 - 电源，单路/双路(±):2.7 V ~ 12 V，±1.35 V ~ 6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:14-TSSOP 包装:剪切带 (CT) 其它名称:OP481GRUZ-REELCT |
| AD8264ACPZ-R7 | 功能描述:IC AMP VGA DIFF QUAD LN 40LFCSP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:50 系列:- 放大器类型:J-FET 电路数:2 输出类型:- 转换速率:3.5 V/µs 增益带宽积:1MHz -3db带宽:- 电流 - 输入偏压:30pA 电压 - 输入偏移:2000µV 电流 - 电源:200µA 电流 - 输出 / 通道:- 电压 - 电源，单路/双路(±):7 V ~ 36 V，±3.5 V ~ 18 V 工作温度:0°C ~ 70°C 安装类型:通孔 封装/外壳:8-DIP（0.300"，7.62mm） 供应商设备封装:8-PDIP 包装:管件 |
| AD8264ACPZ-RL | 功能描述:IC AMP VGA DIFF QUAD LN 40LFCSP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:2,500 系列:Excalibur™ 放大器类型:J-FET 电路数:1 输出类型:- 转换速率:45 V/µs 增益带宽积:10MHz -3db带宽:- 电流 - 输入偏压:20pA 电压 - 输入偏移:490µV 电流 - 电源:1.7mA 电流 - 输出 / 通道:48mA 电压 - 电源，单路/双路(±):4.5 V ~ 38 V，±2.25 V ~ 19 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:带卷 (TR) |
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