tv transmitter circuit 17

  
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A very simple and high quality TV transmitter circuit based on IC MC374 is shown in this article. MC1374 is an integrated TV modulator circuit that can be used in various TV transmitter applications. The MC1374 includes all necessary circuitries required for a TV modulator such as sound carrier oscillator, FM audio modulator, dual input RF modulato
tv transmitter circuit 17 - schematic

r etc. The IC packed with a lot of great features like wide dynamic range, single supply operation, low distortion, variable gain radio frequency modulator section, minimum intermodulation distortion, + or Sync etc. The IC requires few external components and can be operated from a supply voltage range from 5 to 12V DC. The circuit diagram of the TV transmitter using MC1374 is shown below. The video signal input to the circuit can be either negative or positive. The RF output will be approximately zero when the voltages at pin 1 and 11 are equal and the RF output increases linearly as the difference in voltage increases. Resistors R1, R2 and R3 determines the Q factor of the circuit are here their values are so chosen that the Q factor is around 15 which is the desired value for this IC. Resistor R8 connected between pins 12 and 13 sets the modulator gain. The RF output is available from pin 9 which is actually a source which drives a load connected from positive supply line to pin 9. The frequency of the RF oscillator is controlled by the tank circuit comprising of components L1 and C2 connected in association with pins 7 and 6. With the present values of L1 and C2 the RF oscillator frequency is around 105MHz. Components L3, L4, C11, C12 and C13 forms a double pi low pass filter which filters away second harmonics from the radio frequency output. These second harmonics usually occur at very high frequencies due to small...



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