Integratable driver for liquid crystal displays and the like

Claim 1

An integratable circuit for driving a load, comprising: first and second bus means for coupling respectively to first and second electrical potentials; an output terminal for coupling said circuit to said load; a first semiconductor device having first, second and third electrodes; said first electrode being coupled to said first bus means and said second and third electrodes being coupled together and to said output terminal to cause a substantially constant current to flow from said first electrode towards said output terminal; a second semiconductor device having first, second and third electrodes, with the magnitude of the impedance between said first and second electrodes being established by the magnitude of a voltage impressed between said second and third electrodes; said first and second electrodes being respectively coupled to said output terminal and said second bus means respectively; said third electrode receiving a voltage sufficient to reduce the impedance between said first and second electrodes for selectively causing substantially all of said substantially constant current to be conducted to said second bus means through said second semiconductor device responsive only to a first condition; and an avalanche diode coupled between said output terminal and said second bus means for establishing an essentially constant voltage therebetween only when said second semiconductor device responds to a condition other than said first condition and does not conduct substantial current toward said second bus means.