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PDF LM2889N Data sheet ( Hoja de datos )
| Número de pieza | LM2889N | |
| Descripción | LM2889 TV Video Modulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LM2889N (archivo pdf) en la parte inferior de esta página. Total 10 Páginas | ||
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December 1994
LM2889 TV Video Modulator
General Description
The LM2889 is designed to interface audio and video sig-
nals to the antenna terminals of a TV receiver It consists of
a sound subcarrier oscillator and FM modulator video
clamp and RF oscillators and modulators for two low-VHF
channels
The LM2889 allows video information from VTRs video disk
systems games test equipment or similar sources to be
displayed on black and white or color TV receivers
Features
Y Pin for pin compatible with LM1889 RF section
Y Low distortion FM sound modulator (less than 1%
THD)
Y Video clamp for AC-coupled video
Y Low sound oscillator harmonic levels
Y 10V to 16V supply operation
Y DC channel switching
Y Excellent oscillator stability
Y Low intermodulation products
Block and Connection Diagrams (Dual-In-Line Package)
DC Test Circuit
Order Number LM2889N
See NS Package Number N14A
C1995 National Semiconductor Corporation TL H 5079
TL H 5079 – 1
RRD-B30M115 Printed in U S A
1 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
oscillator modulator combination remains off
Circuit Diagrams
TL H 5079 – 5
5
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet LM2889N.PDF ] | |
Hoja de datos destacado
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