| 摘要 |
PURPOSE:To simplify the circuit configuration of a DA converter, by controlling the number of resistances connected in parallel with the 1st and 2nd resistance connected between a power source and earth by means of each bit data of digital signals. CONSTITUTION:A remote control voltage Vr from a transmitter 21 is impressed upon the positive side input of the comparator (CMP) 221 of a receiver 122 and a reference voltage Vs outputted from a DA converter 222 is impressed upon the negative side input of the CMP221. The output of the CMP221 is connected with the input port I of a microcomputer (muCM) 224 through the terminal 223 of the DA converter 222. Resistance R01 and R11 are connected in series between a power source VCC and earth, and an analog reference voltage Vs is outputted from the connecting point of the resistances R01 and R11 to the CMP221. A resistance R02 connected in parallel with the resistance R01 and a diode D1 are controlled by the highest order bit from the muCM224 and resistances R12 and R12 which are connected in parallel with the resistance R11 and controlled by low order bits from the muCM224, respectively, and thus, the voltage Vs is outputted. Bits d0-d2 correspond to the operation of push-buttons S1-S5 of the transmitter stored in an ROM. |
