PURPOSE: To simplify the circuit constitution and at the same time to attain a high-speed addition, the inhibition of a signal delay and the compensation of temperature dependence, by grounding a transistor (TR) for addition to a base and performing the addition of current through the emitter.
CONSTITUTION: A D/A converter 2 is connected to the emitter of an addition TR8 as a constant current source circuit in terms of an equivalent circuit. Then a constant current (i) is converted by an external digital input within a range 0W2I. While an analog input signal ei applied to an input terminal 5 is connected to the emitter of the TR8 to secure variation within a range 0W-2E(-E± E). The operation is started with i=I and i=2I in the case of ei=-E and ei=0, respectively. The emitter current (approximate to collector current) of the TR8 is set approximately at a fixed 2I as well as at a minute signal current Δi based on an error of quantization of the converter 2. This current is converted into the voltage e0 by a resistance 11 and obtained in the form of e0=2IR2+ΔiR2, where 2IR2 and ΔiR2 mean the DC and signal terms, respectively. Thus it is possible to obtain a proper signal output by setting the resistance value R2 at a proper level.
HOTSUTA MASAO
OKIGUCHI KOUTAROU
YOKOYAMA TOSHIHIKO
HITACHI ELECTRONICS
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