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Old 4th Mar 2005, 12:17 pm   #40
ppppenguin
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Default Re: Multi-Channel VHF Modulator Design

I was looking at the audio emitter followers. For video you need to take account of the load as Darius correctly says. If the load is a DC restorer, this can take high-ish current pulses at the sync tips so for -ve syncs a PNP follower is better. If the input of the modulator chip is a keyed clamp the current pulses could be of either polarity. The series resistance definitely does not help a DC restorer but won't make much difference to a keyed clamp unless you are trying to make a very hard clamp. You do not want a hard clamp at the input to a modulator as it will distort the colour burst.
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