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Video Modulator

IP.com Disclosure Number: IPCOM000076567D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 31K

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Arnold, RW: AUTHOR


Video modulator 10 is useful for driving television and other types of display systems.

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Video Modulator

Video modulator 10 is useful for driving television and other types of display systems.

The RF input signal is applied to input 12, c.f. Fig. 1, of differential amplifier T1, T2. In response, the differential amplifier switches the current I, provided by a current source, not shown, at the RF input signal frequency. The collector load of transistor T2 is essentially an L/R parallel network and the collector voltage exhibits the waveshape characteristic shown in Fig. 2. The time periods TR associated with negative going peaks are limited only by transistor switching ability; whereas, the periods associated with the positive going peaks are governed by the L/R time constant. The time constant L/R is judiciously selected so that there is sufficient decay in the collector voltage Vcc to allow the current I to decay to zero.

The output of the amplifier 10 is passed through a low-pass filter R1, R2, and C to provide the output signal go at terminal 13 with a sinusoidal wavechange, c.f. Fig. 3, and at the frequency of the RF input switching signal.


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