參數(shù)資料
型號: THS3001HVIDGNR
廠商: TEXAS INSTRUMENTS INC
元件分類: 音頻/視頻放大
英文描述: 1 CHANNEL, VIDEO AMPLIFIER, PDSO8
封裝: GREEN, PLASTIC, MSOP-8
文件頁數(shù): 13/38頁
文件大?。?/td> 875K
代理商: THS3001HVIDGNR
_
+
RF
RS
RG
eRg
eRf
eRs
en
IN+
Noiseless
IN
eni
eno
e
ni +
en
2
) IN )
R
S
2
) IN–
R
F
R
G
2
) 4 kTRs ) 4 kT RF RG
Where:
k = Boltzmann’s constant = 1.380658
× 1023
T = Temperature in degrees Kelvin (273 +
°C)
RF || RG = Parallel resistance of RF and RG
eno + eni AV + eni 1 )
R
F
R
G
(Noninverting Case)
SLOS217H – JULY 1998 – REVISED SEPTEMBER 2009................................................................................................................................................. www.ti.com
NOISE CALCULATIONS
Noise can cause errors on small signals. This is especially true for amplifying small signals coming over a
transmission line or an antenna. The noise model for current-feedback amplifiers (CFB) is the same as for
voltage feedback amplifiers (VFB). The only difference between the two is that CFB amplifiers generally specify
different current-noise parameters for each input, while VFB amplifiers usually only specify one noise-current
parameter. The noise model is shown in Figure 49. This model includes all of the noise sources as follows:
en = Amplifier internal voltage noise (nV/√Hz)
IN+ = Nonverting current noise (pA/
√Hz)
IN- = Inverting current noise (pA/
√Hz)
eRx = Thermal voltage noise associated with each resistor (eRx = 4 kTRx)
Figure 49. Noise Model
The total equivalent input noise density (eni) is calculated by using the following equation:
To get the equivalent output noise of the amplifier, just multiply the equivalent input noise density (eni) by the
overall amplifier gain (AV).
As the previous equations show, to keep noise at a minimum, small value resistors should be used. As the
closed-loop gain is increased (by reducing RG), the input noise is reduced considerably because of the parallel
resistance term. This leads to the general conclusion that the most dominant noise sources are the source
resistor (RS) and the internal amplifier noise voltage (en). Because noise is summed in a root-mean-squares
method, noise sources smaller than 25% of the largest noise source can be effectively ignored. This can greatly
simplify the formula and make noise calculations much easier.
20
Copyright 1998–2009, Texas Instruments Incorporated
Product Folder Link(s): THS3001
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THS3001HVIDGN 1 CHANNEL, VIDEO AMPLIFIER, PDSO8
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