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CLC4600ISO14X 参数 Datasheet PDF下载

CLC4600ISO14X图片预览
型号: CLC4600ISO14X
PDF下载: 下载PDF文件 查看货源
内容描述: 双,三和四通道300MHz的放大器 [Dual, Triple, and Quad 300MHz Amplifiers]
分类和应用: 商用集成电路放大器
文件页数/大小: 15 页 / 2092 K
品牌: CADEKA [ CADEKA MICROCIRCUITS LLC. ]
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Data Sheet  
General Information - Current Feedback  
Technology  
Advantages of CFB Technology  
V
OUT  
x1  
Z *I  
err  
o
I
err  
The CLCx600 Family of amplifiers utilize current feedback  
(CFB) technology to achieve superior performance. The  
primary advantage of CFB technology is higher slew rate  
performance when compared to voltage feedback (VFB)  
architecture. High slew rate contributes directly to better  
large signal pulse response, full power bandwidth, and  
distortion.  
R
R
g
f
R
L
V
IN  
VOUT  
Rf  
1
=
+
Eq. 2  
V
Rg  
Rf  
Zo(jω)  
IN  
1 +  
CFB also alleviates the traditional trade-off between  
closed loop gain and usable bandwidth that is seen with  
a VFB amplifier. With CFB, the bandwidth is primarily de-  
Figure 2. Inverting Gain Configuration with First Order  
Transfer Function  
termined by the value of the feedback resistor, R . By us-  
f
ing optimum feedback resistor values, the bandwidth of a  
CFB amplifier remains nearly constant with different gain  
configurations.  
CFB Technology - Theory of Operation  
Figure 1 shows a simple representation of a current feed-  
back amplifier that is configured in the traditional non-  
inverting gain configuration.  
When designing with CFB amplifiers always abide by these  
basic rules:  
• Use the recommended feedback resistor value  
Instead of having two high-impedance inputs similar to a  
VFB amplifier, the inputs of a CFB amplifier are connected  
across a unity gain buffer. This buffer has a high imped-  
ance input and a low impedance output. It can source or  
• Do not use reactive (capacitors, diodes, inductors, etc.)  
elements in the direct feedback path  
• Avoid stray or parasitic capacitance across feedback re-  
sistors  
sink current (I ) as needed to force the non-inverting  
err  
input to track the value of Vin. The CFB architecture em-  
ploys a high gain trans-impedance stage that senses Ierr  
• Follow general high-speed amplifier layout guidelines  
and drives the output to a value of (Z (jω) * I ) volts.  
o
err  
• Ensure proper precautions have been made for driving  
capacitive loads  
With the application of negative feedback, the amplifier  
will drive the output to a voltage in a manner which tries  
to drive Ierr to zero. In practice, primarily due to limita-  
tions on the value of Z (jω), Ierr remains a small but  
o
finite value.  
V
IN  
V
OUT  
x1  
Z *I  
o err  
I
err  
A closer look at the closed loop transfer function (Eq.1)  
shows the effect of the trans-impedance, Z (jω) on the  
o
R
f
gain of the circuit. At low frequencies where Z (jω) is very  
R
L
o
large with respect to R , the second term of the equation  
f
R
g
approaches unity, allowing R and R to set the gain. At  
f
g
higher frequencies, the value of Z (jω) will roll off, and  
o
the effect of the secondary term will begin to dominate.  
The -3dB small signal parameter specifies the frequency  
VOUT  
Rf  
1
=
1 +  
+
Eq. 1  
where the value Z (jω) equals the value of R causing the  
o
f
V
Rg  
Rf  
Zo(jω)  
IN  
1 +  
gain to drop by 0.707 of the value at DC.  
For more information regarding current feedback ampli-  
fiers, visit www.cadeka.com for detailed application notes,  
such as AN-3: The Ins and Outs of Current Feedback Am-  
plifiers.  
Figure 1. Non-Inverting Gain Configuration with First  
Order Transfer Function  
©2004-2008 CADEKA Microcircuits LLC  
www.cadeka.com  
9
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