Widlar current source

Abstract: This invention provides a display apparatus in which it is possible to have a light emitting element emitted light with constant luminance without coming under the influence of deterioration over time, and it is possible to realize accurate gray scale express, and yet, it is possible to speed up writing of a signal current to each pixel, and influence of noise of a leak current etc is suppressed, and a driving method thereof A plurality of pairs of switch parts and current source circuits are disposed in each pixel Switching of each of a plurality of the switch parts is controlled by a digital video signal When the switch part is turned on, by a current supplied from the current source circuit making a pair with the switch part, the light emitting element emits light A current which is supplied from one current source circuit to the light emitting element is constant A value of a current flowing through the light emitting element is comparable to a value of added currents which are supplied to the light emitting element from respective all current source circuits making pairs with the switch parts which are in the conductive states

Abstract: A constant current driver with auto-clamped pre-charge function includes a reference bias generator and a plurality of constant current driver cells, each being connected to the reference bias generator to form a respective current mirror. Each constant current driver cell has a switch transistor, a current output transistor and a pre-charge transistor. When a constant current is outputted from the current output transistor for driving an organic light emitting diode, the pre-charge transistor is turned on to provide a drain to source current as an additional large current for rapidly pre-charging the organic light emitting diode until the gate to source voltage of the pre-charge transistor is smaller than the threshold voltage.

Abstract: A digital-to-analog converter of the type formed with a plurality of current source transistors arranged to carry different levels of current according to a predetermined weighting pattern, e.g., a binary weighting pattern. In the converter, a plurality of identically sized current source transistors carry the different levels of current and thus operate at different current densities with different base-to-emitter voltages subject to temperature drift. Stable emitter voltages, providing accurate levels of weighted current, are developed by means of resistances between the bases of successive current source transistors and a current source for developing across the interbase resistances a voltage linearly varying with absolute temperature, corresponding to the difference between base-to-emitter voltages of the successive current source transistors. The apparatus for generating a current linearly varying with absolute temperature is formed with first and second transistors forced to carry the same current at different current densities to produce different base-to-emitter voltages, and means such as an emitter resistor responsive to the difference in the base-to-emitter voltages for developing a current, corresponding to the difference in base-to-emitter voltages, which varies linearly with temperature.

Abstract: The invention relates to a dimmer triggering circuit (12) for triggering a dimmer in an alternating current network. The dimmer has a voltage-level detector (15), and a bipolar current source circuit (18). The voltage-level detector (15) detects whether an absolute value of an input voltage of the dimmer triggering circuit is below a threshold value. The bipolar current source circuit (18) provides a current if the voltage detected by the voltage-level detector (15) is below the threshold value. If the voltage detected is not below the threshold value, the bipolar current source circuit is deactivated. The dimmer triggering circuit (12), in operation, dissipates an average power less than 100 mW.