Title: R.F. modulator for use in T.V. games

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Abstract: An N-channel MOS monolythic R.F. Modulator for use in television games or the like is provided which internally generates an R.F. carrier signal and modulates same in accordance with the composite video output signal from the T.V. interface chip. The modulator utilizes two depletion mode MOSFETs connected in a cascode configuration, the output circuits of which are connected in series with an inductor, between a voltage source and ground. The input terminal of one of the transistors receives the composite video signal. The input terminal of the second transistor is connected to a resonant frequency circuit. The resonant frequency circuit is electromagnetically coupled to the inductor such that the current flowing through the inductor impresses a current in the resonant frequency circuit to cause same to generate the R.F. carrier signal. The magnitude of the video signal varies the conductance of the transistor output circuit thereby varying the current through the inductor and thus the amplitude of the carrier signal in the resonant frequency circuit. An output inductor is also electromagnetically coupled to the resonant frequency circuit to receive the amplitude modulated carrier signal therefrom in order to provide a low impedance output.


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