Passive LCD vs Active LCD and PMOLED vs AMOLED

 

Passive LCD vs. Active LCD 

Passive Matrix LCD uses grid of vertical and horizontal conductors comprised of ITO( Indium Tin Oxide) to create an image. Each pixel is controlled by an intersection of two conductors. By creating a potential voltage difference at an intersection, the LC fluid is able to respond by creating an “on” state at that intersection, also commonly referred to as a pixel. Please see the structure of passive LCD as below.

Fig. 1 Passive Matrix LCD Structure

Active-Matrix LCD uses TFT (thin film transistors) that are arranged in a matrix on a glass surface. To control the voltage tiny switching transistors and capacitors are used at each pixel location. The active pixel is called so because it has the ability to control the individual pixels and switch them quickly. Please see the active matrix LCD structure below.

Fig. 2 Active Matrix LCD Structure

Fig. 3 Passive Matrix LCD and Active Matrix LCD Driving Comparison

 

Difference Between Passive Matrix LCD and Passive Matrix LCD

	Passive Matrix LCD	Active Matrix LCD
Structure	It uses grid of vertical and horizontal conductors comprised of Indium Tin Oxide to create an image. Each pixel is controlled by an intersection of two conductors.	It uses thin film transistors that are arranged in a matrix on a glass surface. To control the voltage tiny switching transistors and capacitors are used at each pixel location.
Cost	Lower	Higher
Customization	Flexible with lower cost	Higher NRE with $100K to $1M
Contrast Ratio	Lower	Higher
Response time	Slower	Faster
Color Saturation	Lower, not true color	Higher
Resolution	Limited to 320×240 with reasonable contrast	Capable for much higher resolution, can produce 8K resolution now.
Gray scale	Very limited	Capable for high gray scale
Current Consumption	Lower	Higher
Application	Low cost watches, calculators, utility meters etc. Mainly low cost, low power monochrome displays	Laptop, monitor, mobile phones, TVs, ATM, Kiosk, Advertisement panels etc. Mainly color displays

 

PMOLED vs. AMOLED

OLEDs are made from organic light-emitting materials that emit light when electricity is applied. OLED displays are emissive. That is the reason that OLED displays do not require backlight or filtering that are used in LCDs. As a result, OLEDs can be made flexible and transparent while providing the best images and great contrast and view angles.

Similar to LCD displays having two types: Passive Matrix LCD and Active-Matrix LCD, OLED displays also has two types: PMOLED and AMOLED. The difference is in the driving electronics – it can be either Passive Matrix (PM) or Active Matrix (AM).

Similar to passive matrix LCD, a PMOLED display uses a simple control scheme in which you control each row (or line) in the display sequentially (one at a time). PMOLED electronics do not contain a storage capacitor and so the pixels in each line are actually off most of the time. Because of this ,more voltage is needed to make PMOLED brighter. If you have 10 lines, for example, you have to make the one line that is on 10 times as bright (the real number is less than 10, but that’s the general idea).

While PMOLEDs are easy and low cost to produce, they are not efficient and the OLED materials suffer from lower lifetime (due to the high voltage needed). PMOLED displays are also restricted in resolution and size (the more lines you have, the more voltage you have to use). PMOLED displays are usually small (up to 2″ in color and 6” in monochrome typically) and can be used in simple digits/icons, characters, alphanumeric and low resolution dot matrix application such as  a MP3 players, mobile phone sub displays, simple waist watch etc.