参数资料
| 型号： | ADL5304ACPZ-RL |
| 厂商： | Analog Devices Inc |
| 文件页数： | 11/32页 |
| 文件大小： | 0K |
| 描述： | IC AMP LOG CONV 32LFCSP |
| 标准包装： | 5,000 |
| 类型： | 对数转换器 |
| 应用： | 光纤 |
| 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（5x5） |
| 包装： | 带卷 (TR) |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页当前第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
Data Sheet
ADL5304
Rev. 0 | Page 19 of 32
Bandwidth vs. Current
Assuming a 20 kHz net system bandwidth at this current, the
integrated noise voltage is 70 μV rms. The theoretical noise of
of 10 mV/dB at the VLOG pin. Therefore, the noise at VLOG,
predicted by Equation 22, is multiplied by a factor of 3.33.
Secondary sources of noise, mostly in the analog divider used
for temperature stabilization of the slope and the input FET
buffer amplifiers, add to this basic noise. The measured data are
shown in Figure 22.
Both the response time and wideband noise of translinear log
amps are functions of the transistor collector current, IC, and
only slightly amenable to improvement by circuit design. The
bandwidth falls at low values of IC due to the effects of junction
capacitances in Q1 and the decrease in transconductance (gm)
of a bipolar transistor, which is a linear function of IC, or in the
case of a photodiode application, the photocurrent, IPD. The
corresponding incremental emitter resistance is
re = 1/gm = VT/IPD = kT/qIPD
(20)
Note how at low frequencies the NSD flattens for input currents
less than 10 nA, this noise is limited by the resistor that makes
the dc current. A 10 MΩ resistor was used for these three currents
with a dc bias voltage across the resistor of 1 mV, 10 mV, and
100 mV, respectively.
and becomes extremely high at low currents (260 MΩ at IC =
100 pA). Therefore, even minute capacitances associated with
the transistor can generate very long time constants.
If the net effect of these capacitances is represented loosely as
CJ, the corresponding low-pass corner frequency is
A 10 MΩ resistor makes a noise current of 40.7 fA/√Hz, which is
converted via the gm of the logging transistor into a noise voltage.
This voltage adds to the noise voltage of the bipolar transistor itself,
to 25.85 MΩ at IC equals 1 nA. Together with the noise current of
the source resistor, this makes a noise voltage at the emitter of the
logging transistor (VNUM) of 1.05 μV/√Hz; this contrasts with
the noise voltage of the transistor itself of 0.46 μV/√Hz
(~0.5 μV/√Hz). The total combined noise is ~1.15 μV/√Hz.
f3dB = qIPD/2πkTCJ
(21)
showing the proportionality of bandwidth to current. Using a
value of 0.3 pF for CJ, this becomes 20 MHz/μA. The small signal
bandwidth at IPD = 100 pA is thus only 2 kHz. However,
whereas this simple model can be useful in making the basic
point, it excludes many other effects that limit its accuracy. At high
currents, the subsequent signal processing limits the maximum
overall bandwidth.
Noise vs. Current
The effect of the 10 MΩ resistor at 100 pA of dc current becomes
even more pronounced because the noise at VNUM due to the
source resistor is 10.5 μV/√Hz, whereas the transistor only
contributes 1.46 μV/√Hz for a total of 10.6 μV/√Hz.
For an ideal bipolar transistor, the voltage noise spectral density,
SNSD, referred to VBE, and caused by shot-noise mechanisms,
evaluates to
Therefore, unless the resistor that makes the dc current becomes
very large, in general, measurement at the lower currents is
limited by the noise of the source resistor. This problem does not
exist when using a photodiode because the resistance of the
photodiode increases at the same rate as the logging transistor
(see Figure 47).
SNSD = 14.6/√IC nV/√Hz (TA = 27°C)
(22)
where IC is in μA. For example, at an IC of 1 nA, SNSD evaluates to
approximately 0.5 μV/√Hz.
10V
1V
100nV
10nV
1nV
100pV
100p
1n
10n
100n
1
10
100
1m
10m
N
O
ISE
SPEC
T
R
A
L
D
E
N
S
IT
Y
(V
/
Hz
)
IC (A)
09
45
9-
0
56
NOISE SPECTRAL DENSITY OF VBE
Figure 46. Noise Spectral Density of VBE vs. IC
相关PDF资料 |
PDF描述 |
|---|---|
| ADL5310ACP-R2 | IC LOGARITHMIC CONV DUAL 24LFCSP |
| ADN3000-06-50A-PT | IC AMP TRANSIMPEDANCE DIEFORM |
| ADN4670BSTZ | IC CLOCK BUFFER MUX 2:10 32LQFP |
| ADS7864YB/250G4 | IC 12BIT 500KHZ 6CH ADC 48-TQFP |
| ADS7883SBDBVR | IC ADC 12-BIT 3MSPS SOT23-6 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ADL5304-EVALZ | 功能描述:BOARD EVAL FOR ADL5304A RoHS:是 类别:编程器，开发系统 >> 评估演示板和套件 系列:* 标准包装:1 系列:- 主要目的:电信，线路接口单元（LIU） 嵌入式:- 已用 IC / 零件:IDT82V2081 主要属性:T1/J1/E1 LIU 次要属性:- 已供物品:板，电源，线缆，CD 其它名称:82EBV2081 |
| ADL5305ACP-REEL | 制造商:Analog Devices 功能描述:LOGARITHMIC CONVERTER - Tape and Reel |
| ADL5306 | 制造商:AD 制造商全称:Analog Devices 功能描述:60 dB Range (100 nA to 100 UA) Low Cost Logarithmic Converter |
| ADL5306ACP | 制造商:AD 制造商全称:Analog Devices 功能描述:60 dB Range (100 nA to 100 UA) Low Cost Logarithmic Converter |
| ADL5306ACP-R2 | 功能描述:IC CONVERT LOGARITH 60DB 16LFCSP RoHS:否 类别:集成电路 (IC) >> 线性 - 放大器 - 专用 系列:- 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 |
发布紧急采购，3分钟左右您将得到回复。