TSH70CD(2002) 查看數據表（PDF） - STMicroelectronics
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TSH70CD
(Rev.:2002)
(Rev.:2002)
STMicroelectronics
TSH70CD Datasheet PDF : 25 Pages
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TSH70, 71, 72, 73, 74, 75
Parameter
Phase Margin
f-3dB
Phase Margin
f-3dB
Phase Margin
f-3dB
Phase Margin
f-3dB
Cf (pF)
0
5.6
22
33
Example of a video application :
Vcc=!1.5V
28
40
30
40
37
37
48
33.7
Vcc=!2.5V
43
39.3
43
39.3
52
34
65
30.7
Vcc=!5V
56
38.3
56
38.3
67
32
78
27.6
Unit
deg
MHz
deg
MHz
deg
MHz
deg
MHz
Vcc/2
IN
Ce Rb1 AOP1
+ V1
-
Re
R2
R1 Cf
Vcc/2
R3 C3
V2
PAL
V3
A1
R4
LPF1
R7 C7
NTSC
A2
R8
LPF2
Vcc/2
C4 Rb1
+ AOP2
-
R6
Vcc/2 R5
Vcc/2
C8 Rb1
Cf
Standby
+ AOP3
-
R10
Rout Cout OUT
V4
RL
Vcc/2 R9
Cf
Standby
This example shows a possible application of the TSH7X circuit. Here, you can multiplex the channels for
the different standard PAL, NTSC as you filter for the different bands; the video signal can be filtered with
two different cutoff frequencies, corresponding to a PAL encoded signal (LPF1) or a NTSC signal (LPF2).
You can multiplex input signals, as the outputs are in high impedance state in standby mode.This enables
you, to use a PAL filter as the Standby mode is active and to use the NTSC filter otherwise.
The video application requires 1Vpeak at input and output.
Calculation of components:
A decoupling capacitor is provided to cutoff the frequencies below 10Hz according I bias.Hence Ce=10uF,
with Rb1=10KΩ. At the output, Cout=220uF.
The AOP1 is in 6dB configuration for the adaptation bridge. R1=R2=1KΩ.V1=2Vpk. V2=1Vpk
For the PAL communication, we need a lowpass filtering. The load resistance R4 is function of the output
resistance of the filter.V3=V2/A1 where A1 is the attenuation factor of the filter LPF1.
To compensate the filter insertion loss, we add an additional factor to the gain of the 2nd amplifier AOP2.
For example, for an attenuation of 3dB, we choose R5=300Ω and R6=1KΩ. We have V4=2Vpk and
Vout=1Vpk.
The calculation of the parameters R7, C7, R8, C8, R9, R10 will be exactly the same .
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