GS1881_09 Datasheet, PDF (24/29 Pages) Gennum Corporation – Monolithic Video Sync Separators

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SERIES RESISTOR (Ω)
Figure 5-6: VCLIP vs Series Resistor
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SERIES RESISTOR (Ω)
Figure 5-7: Cƒ vs Series Resistor
600 700
Another way to minimize the amount of attenuation is to control the source resistance
seen by the sync separator by using a PNP emitter follower (Figure 5-8). A PNP emitter
follower works well to drive the sync separator, and does not require much DC current
because the transistor provides the current when it is needed during sync. Figure 5-9 is
a typical application circuit that minimizes sync tip clipping.
V_CC
VIDEO
INPUT
FILTER
75Ω
5.6k
C_C
-5V
8
2
6
4
680k _0.1μ
Figure 5-8: PNP Emitter Follower Buffer
GS1881, GS4881, GS4981 Monolithic Video Sync
Separators
Data Sheet
6926 - 5
November 2009
24 of 29
Proprietary & Confidential