Current-regulated field emission cathodes for use in a flat panel display in which low-voltage row and column address signals control a much higher pixel activation voltage

• US 5,357,172 A
• Filed: 02/01/1993
• Issued: 10/18/1994
• Est. Priority Date: 04/07/1992
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Lowrey, Tyler A., Casper, Stephen L., Lee, John K.
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US08/011,927
• Time in Patent Office: 624 Days
• Field of Search: 315/169.1, 315/169.3, 315/169.4, 315/320, 315/325, 315/334, 315/349, 315/337, 315/339, 315/167, 315/DIG. 7
• US Class Current: 315/167
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: H01J 31/127 using large area or array sources, i.e. essentially a source for each pixel group
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

In a flat panel display in which low-voltage row and column address signals control a much higher pixel activation voltage by respectively gating at least one pair of series coupled MOSFETs to ground for each pixel, effective current regulation is achieved by placing a current-regulating resistor in series with each pair of the series-coupled MOSFETs. The resistor is coupled directly to ground and to the source of the MOSFET furthest from the emitter node. By coupling the current-regulating resistor directly to the ground bus, stable current values are achieved over a wide range of cathode voltages.

Claims

1. A current-regulated field emission display comprising:

multiple row address lines;

multiple column address lines;

said row address lines intersecting said column address lines, with the intersection of a single row address line with a single column address line being associated with a single pixel within said display;

a grid which is common to the entire display, and which is held at a first potential;

groups of field emission cathodes, each group being associated with a particular pixel, each group being maintained at a second potential during periods of pixel inactivation, said second potential being close enough to said first potential so as to suppress field emission, and each group being maintained at a third potential during periods of pixel activation, said third potential being sufficiently low, with respect to said first potential, to induce field emission;

at least one pull-down current path between the cathode group of each pixel and a node held at a fourth potential that is less than or equal to said third potential, said path comprising a current-regulating resistor and at least two field-effect transistors, said resistor and said transistors being series coupled, with said resistor being directly coupled to said node, at least one of said transistors being activatable in response to a signal on pixel'"'"'s respective row address line, at least one other transistor being activatable in response to a signal on a that pixel'"'"'s respective column address line, so as to enable switching of the potential applied to the cathode group associated with that pixel between said second potential and said third potential.

2. The current-regulated field emission display of claim 1, wherein said node is maintained at ground potential.

3. The current-regulated field emission display of claim 1, wherein each cathode group associated with a particular pixel is comprised of multiple cathode subgroups, each subgroup having its own pull-down current path.

4. A current-regulated, vacuum micro-electronic triode comprising:

a grid which is continuously maintained at a first potential;

a field emission cathode to which a second potential or a third potential may be selectively applied, said second potential being close enough to said first potential so as to suppress field emission, said third potential being sufficiently low, with respect to said first potential, to induce field emission;

a pull-down current path between the cathode and a node held at a fourth potential that is less than or equal to said third potential, said path comprising a current-regulating resistor and at least one field-effect transistor, said resistor and said transistor being series coupled, with said resistor being directly coupled to said node, said transistor being selectively activatable so as to enable selective application of said second potential or said third potential to said cathode.

5. The current-regulated vacuum micro-electronic triode of claim 4, wherein said pull-down current path comprises a current-regulating resistor and two field-effect transistors, one of said transistors being activatable in response to a row address signal, and the other of said transistors being activatable in response to a column address signal.