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Q: What differentiates passive matrix LCDs from active matrix LCDs?
A: An LCD is made with either a passive matrix or an active matrix display grid. An active
matrix has a transistor located at each pixel intersection, requiring less current to control
the luminance of a pixel. For this reason, the current in an active matrix display can be
switched on and off more frequently, improving the screen refresh time (your mouse pointer
will appear to move more smoothly across the screen, for example). The passive matrix LCD
has a grid of conductors with pixels located at each intersection in the grid.
Q: How does a TFT LCD Panel work?
A: On each column and row of the TFT LCD panel, a data source drive and a gate drive are
attached, respectively. The TFT drain of each cell is connected to the electrode. The
molecular arrangement of liquid crystal elements differ according to whether it is impressed
with voltage or not. It varies the direction of polarized light and the amount of light by letting
it through different arrays of liquid crystal elements. When two polarized filters are arranged
vertically on a polarized light pole, the light that passes through the upper polarized panel is
turned 90 degrees along with the spiral structure of the liquid crystal molecules and goes
through the polarized filter at the bottom. When impressed with voltage, liquid crystal
molecules are arranged vertically from the original spiral structure and the direction of the
light is not turned through 90 degrees. In this case, light that comes through the top
polarized panel may not go through the polarized panel at the bottom.
Q: What are the advantages of TFT LCD compared with CRT?
A: In a CRT monitor, a gun shoots electrons and general light by colliding polarized
electrons on fluorescent glass. Therefore, CRT monitors basically operate with an analog
RGB signal. A TFT LCD monitor is a device that displays an input image by operating a
liquid crystal panel. The TFT has a fundamentally different structure than a CRT: Each cell
has an active matrix structure and independent active elements. A TFT LCD has two glass
panels and the space between them is filled with liquid crystal. When each cell is connected
with electrodes and impressed with voltage, the molecular structure of the liquid crystal is
altered and controls the amount of inlet lighting to display images. A TFT LCD has several
advantages over a CRT, since it can be very thin and no flickering occurs because it does
not use the scanning method.
Q: Why is vertical frequency of 60Hz optimal for an LCD monitor?
A: Unlike a CDT monitor, the TFT LCD panel has a fixed resolution. For example, an XGA
monitor has 1024x3 (R, G, B) x 768 pixels and a higher resolution may not be available
without additional software processing. The panel is designed to optimize the display for a
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