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Very‐sensitive direct measurement of plasma‐display exoemission
Author(s) -
Weber Larry F.,
Yan Qun Frank
Publication year - 2011
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1889/jsid19.2.212
Subject(s) - cathode , waveform , amplifier , plasma display , materials science , direct current , plasma , current (fluid) , voltage , electrical impedance , displacement current , optoelectronics , electron , capacitance , signal (programming language) , relay , electrical engineering , physics , computer science , power (physics) , electrode , cmos , quantum mechanics , programming language , engineering
— The exoemission of electrons from the MgO cathode surface has a great impact on many properties of plasma displays and needs to be carefully engineered for successful display products. A method for direct measurement of this exoemission current using an ultra‐high‐impedance amplifier, which detects the integrated exoemission charge collected by a capacitance, is presented. The large discharge and displacement currents initiated by the changing sustain waveform, which could overload and saturate the sensitive amplifier, are shorted by a very low impedance switch in the form of a common reed relay. The exoemission current from the MgO cathode is significantly amplified by avalanches in the gas, and thus methods for directly measuring the avalanche amplification factor so as to correct the measured current and obtain the true exoemission current from the cathode are described. This highly variable avalanche amplification factor is measured and estimated to be as large as 500 when the voltage across the gas is just below breakdown. Methods are covered to correct for the small ion currents that flow in the plasma‐panel soda glass substrates and that add an unwanted error signal. Practical circuit techniques for measuring the very small exoemission currents are presented.