Patent ID: 8890545
Filing Date: 2014-11-18
Classification: G09G

Abstract:
1. A display system comprising: a display substrate having formed thereon a plurality of pixels, gate line drivers, and data line drivers, wherein the pixels and the gate and data line drivers have an original transistor formed on the substrate, the original transistor being a constituent part of one of the pixels, at least one of the gate line driver and the data line driver being driven by a transistor drive circuit; a replica transistor formed on the substrate that is a replica of the original transistor and is coupled to be driven so as to emulate the original transistor; a ring oscillator test circuit having a ring of inverters coupled to the replica transistor to produce an oscillation frequency with and without the replica transistor coupled to the oscillator ring; a frequency measurement circuit to measure the frequency of the ring oscillator circuit with and without the replica transistor coupled to the oscillator ring to determine an indication of the threshold voltage of the replica transistor based on the measured frequency; and a compensation facility in the transistor drive circuit to adjust the voltage applied to the original transistor based on the replica transistor threshold voltage.