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LM2889N データシート(PDF) 5 Page - National Semiconductor (TI) |
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LM2889N データシート(HTML) 5 Page - National Semiconductor (TI) |
5 / 10 page Circuit Description (Refer to Circuit Diagrams) The sound carrier oscillator is formed by differential amplifi- er Q3 Q4 operated with positive feedback from the pin 13 tank to the base of Q4 Frequency modulation is obtained by varying the 90 degree phase shifted current of Q9 Q14’s emitter is a virtual ground so the voltage at pin 1 deter- mines the current R11 which ultimately modulates the col- lector current of Q9 The video clamp is comprised of devices Q58-Q60 The clamp voltage is set by resistors R40 R41 R49 and R50 The DVBE R42 current sets the capacitor discharge cur- rent Q59 and the above mentioned resistor string help maintain a temperature stable clamp voltage The channel B oscillator consists of devices Q24 and Q25 cross-coupled through level-shift zener diodes Q22 and Q23 A current regulator consisting of devices Q17 – Q21 is used to achieve good RF stability over temperature and supply The channel B modulator consists of multiplier de- vices Q28 – Q31 Q34 and Q35 The top quad is coupled to the channel B tank through isolating devices Q26 and Q27 A DC potential between pins 10 and 11 offsets the lower pair to produce an output RF carrier at pin 8 That carrier is then modulated by both the sound subcarrier at pin 10 and the composite video signal at pin 11 The channel A modu- lator shares pin 10 and 11 buffers Q32 and Q33 with chan- nel B and operates in an identical manner The current flowing through channel B oscillator diodes Q22 Q23 is turned around in Q36 – Q38 to source current for the channel B RF modulator In the same manner the channel A oscillator Q54 – Q57 uses turn-around Q49 – Q51 to source the channel A modulator One oscillator at a time may be activated by its current turn-around and the other oscillatormodulator combination remains off Circuit Diagrams TLH5079 – 5 5 |
同様の部品番号 - LM2889N |
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同様の説明 - LM2889N |
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