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KH563 参数 Datasheet PDF下载

KH563图片预览
型号: KH563
PDF下载: 下载PDF文件 查看货源
内容描述: 宽带,低失真驱动器放大器 [Wideband, Low Distortion Driver Amplifier]
分类和应用: 驱动器放大器
文件页数/大小: 13 页 / 261 K
品牌: CADEKA [ CADEKA MICROCIRCUITS LLC. ]
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KH563  
DATA SHEET  
For the circuit of Figure 1, the equivalent input noise  
voltage may be calculated using the data sheet spot  
noises and R = 25, R = . Recall that 4kT = 16E-21J.  
R'o = Rx + Ro  
Rx  
Vi  
+
Cx  
Rs  
s
L
KH563  
Vo  
All terms cast as (nV/Hz)2  
RL  
Ro = R'o - Rx  
-
Rf  
2
2
2
2
2
2
e = 2.1 + .07 + .632 + 1.22 + .759 + .089  
(
)
(
)
(
)
(
)
(
)
(
)
n
With:  
Ro = KH563 output impedance  
and R + Rx = RL generally  
Rg  
= 2.62nV/ Hz  
o
Gain Accuracy (DC):  
A classical op amp’s gain accuracy is principally set by  
the accuracy of the external resistors. The KH563  
also depends on the internal characteristics of the  
forward current gain and inverting input impedance. The  
performance equations for A and R along with the  
Figure 9: Improving Output Impedance  
Match vs. Frequency  
Increasing R will decrease the achievable voltage swing  
x
at the load. A minimum R should be used consistent  
v
o
x
Thevinin model of Figure 5 are the most direct way of  
assessing the absolute gain accuracy. Note that internal  
temperature drifts will decrease the absolute gain  
slightly as the part warms up. Also note that the para-  
meter tolerances affect both the signal gain and output  
impedance. The gain tolerance to the load must include  
both of these effects as well as any variation in the load.  
The impact of each parameter shown in the performance  
with the desired output match. As discussed in the  
thermal analysis discussion, R is also very useful in  
x
limiting the internal power under an output shorted  
condition.  
Interpreting the Slew Rate:  
The slew rate shown in the data sheet applies to the volt-  
age swing at the load for the circuit of Figure 1. Twice this  
value would be required of a low output impedance  
amplifier using an external matching resistor to achieve  
the same slew rate at the load.  
equations on the gain to the load (A ) is shown below.  
L
Increasing current gain G  
Increasing inverting input R  
Increases A  
L
Decreases A  
i
L
Layout Suggestions:  
Increasing R  
Increasing R  
lncreases A  
Decreases A  
f
L
The fastest fine scale pulse response settling requires  
careful attention to the power supply decoupling.  
Generally, the larger electrolytic capacitor ground  
connections should be as near the load ground (or cable  
shield connection) as is reasonable, while the higher  
frequency ceramic de-coupling caps should be as near  
the KH563’s supply pins as possible to a low inductance  
ground plane.  
g
L
Applications Suggestions  
Driving a Capacitive Load:  
The KH563 is particularly suitable for driving a capacitive  
load. Unlike a classical op amp (with an inductive output  
impedance), the KH563’s output impedance, while  
starting out real at the programmed value, goes some-  
what capacitive at higher frequencies. This yields a very  
stable performance driving a capacitive load. The overall  
response is limited by the (1/RC) bandwidth set by the  
KH563’s output impedance and the load capacitance. It  
Evaluation Boards:  
An evaluation board (showing a good high frequency lay-  
out) for the KH563 is available. This board may be  
ordered as part #730019.  
is therefore advantageous to set a low R with the  
o
constraint that extremely low R values will degrade the  
Thermal Analysis and Protection  
f
distortion performance. R = 25was selected for the  
A thermal analysis of a chip and wire hybrid is  
directed at determining the maximum junction  
temperature of all the internal transistors. From the total  
internal power dissipation, a case temperature may be  
developed using the ambient temperature and the case  
to ambient thermal impedance. Then, each of the  
dominant power dissipating paths are considered to  
determine which has the maximum rise above case  
temperature.  
o
data sheet plots. Note from distortion plots into a  
capacitive load that the KH563 achieves better than  
60dBc THD (10-bits) driving 2V  
through 30MHz.  
into a 50pF load  
pp  
Improving the Output Impedance Match  
vs. Frequency - Using R :  
x
Using the loop gain to provide a non-zero output  
impedance provides a very good impedance match at  
low frequencies. As shown on the Output Return Loss  
plot, however, this match degrades at higher frequencies.  
Adding a small external resistor in series with the output,  
The thermal model and analysis steps are shown below.  
As is typical, the model is cast as an electrical model  
where the temperatures are voltages, the power dissipa-  
tors are current sources, and the thermal impedances  
are resistances. Refer to the summary design equations  
and Figure 1 for a description of terms.  
R , as part of the output impedance (and adjusting the  
x
programmed R accordingly) provides a much better  
o
match over frequency. Figure 9 shows this approach.  
REV. 1A January 2008  
11