How do passive-matrix LCDs differ from active-matrix LCDs?
In nematic arrangements the crystals are randomly positioned with all their long axes pointing in essentially the same direction, given by a vector known as the director. In smectic arrangements the crystals are further constrained to parallel planes; in smectic A the director is perpendicular to these planes, while in smectic C the director is at some other angle to the planes.
The primary difference between passive-matrix and active-matrix liquid crystal displays (LCDs) lies in how they control individual pixels to create images.
Passive-Matrix Displays
In a passive-matrix display, pixels are controlled in groups. This method uses a grid of electrodes to address rows and columns of pixels. Because the pixels lack individual switching components, the display is limited in its ability to produce high-resolution, complex images; for instance, traditional passive-matrix twisted nematic (TN) displays are generally restricted to producing images with only about 20 rows of pixels.12
Active-Matrix Displays
Active-matrix displays, such as those using thin-film transistor (TFT) technology, provide superior performance for complex, high-resolution images. In these displays, each individual pixel is associated with its own silicon transistor, which acts as a dedicated electronic switch. This grid of thousands of transistors and capacitors allows for precise, rapid control over specific portions of the liquid crystal. By enabling each pixel to be addressed independently, active-matrix technology supports the high-resolution requirements of modern computer monitors and televisions.34