Multiple-valued current mode adder implemented by transistor having negative transconductance

A multiple-valued current-mode adder for adding a plurality of integers, comprising:

• (a) a summing node where a plurality of currents are merged, the amounts of said currents being representative of values of said integers, respectively;
• (b) an input current-to-voltage converter coupled to said summing node and operative to convert the total amount of said currents into an input voltage level, said input voltage level being within a predetermined range;
• (c) a transistor having a negative transconductance with a turning point the voltage level of which is within said predetermined range, said transistor being supplied with said input voltage level and producing a first output current in accordance with said input voltage level and said negative transconductance;
• and
• (d) a threshold value detecting circuit supplied with said input voltage level and producing a second output current in accordance with said input voltage level, said second output current varying at a certain point from a first value to a second value and the voltage level of said certain point being within said predetermined range.