ANALOG ARITHMETIC UNIT

PURPOSE:To obtain an analog arithmetic unit with a small circuit scale without the limit of the number of bits of a digital input signal. CONSTITUTION:Current control current source circuits 1, 2, 3 are provided, which generate an output current obtd. by multiplying current amplification factors A1, A2, A3 by an input current in response to a control input C1 and a reset control input C2. The input current of the circuit 1 is a current I0 of a reference current source 4 and control inputs C1, C2 are digital signals D, and the inverse of D. Sum of the output current IOUT1 of the circuit 1 and the output current IOUT3 of the circuit 3 is used for an input current to the circuit 2 and the output current IOUT2 of the circuit 2 is used for the input current of the circuit 3. The circuits 2, 3 are operated alternately by clock signals CC, and the inverse of CC and the circuit 2 is reset by a reset signal RST before a series of digital signals D, and the inverse of D.