Semiconductor switching circuit for controlling LCD Indicators - uses IIL logic circuitry and driver transistors for low current consumption and fast switching

摘要

The switching circuit for the LCD control consists of an input (SE) into a logic decoder or multiplexer (L) which is constructed from IIL logic, having inverting qualities and characteristics of a NOR or NAND gate. Each output (LA1,LA2,LA3) of the logic circuit (L) switches a constant current source, which serves to drive the base of its respective transistor (T1,T2,T3) the emitters of which are fed from three stepped operating voltages, where U1 equals 1 volt, U2 equals 2 volts, and U3 equals 3 volts. The output (A) is common to the collectors of the driver transistors (T1,T2,T3), and a complimentary transistor (t), whose emitter is at the reference potential (Uo), with the base controlled by the logic circuit (L), also has its collector common to the output (A). This circuit using IIL elements consumes little current, is fast acting and operates on low voltage which is essential for portable apparatus such as a calculator etc.