Driving circuit for a fluorescent display apparatus having fewer leads

Claim 1

A fluorescent display apparatus comprising: a vacuum casing made up of a substrate and a front cover airtightly bonded together; a plurality of anodes each coated with a phosphor layer on the upper surfaces thereof and disposed on said substrate; said anodes being divided into consecutive several groups so as to include a certain number of anodes in each of said anode groups; each of said anodes disposed in corresponding positions of said respective anode groups being connected together in parallel; a plurality of control electrodes each provided in an opposite relationship with respect to said respective anode groups; a filamentary cathode stretched above said control electrodes for emitting thermions when energized and heated; a first decoder means for decoding the least significant digit of an input signal and for driving a plurality of anodes having corresponding positions in said respective anode groups with a continuous signal; and a second decoder means for decoding at least one more significant digit of said input signal and for driving one of said control electrodes with a continuous signal, whereby one of said anodes selected by said first and second decoders representing the value of said input signal is illuminated and said fluorescent display apparatus is substantially noise-free.