| 摘要 |
PURPOSE:To obtain a converting circuit whose converting accuracy is not easily affected by the fluctuation of a digital signal level. CONSTITUTION:For instance, if only binary signals D1 and D2 are set at a high level, the FETQ1 and Q2 are turned on. Then two current corresponding to the FETQ1 and Q2 are produced between the inverted input terminal (-) of an operational amplifier and an earth point GND. The input current is very small and can be neglected at the amplifier OP1 and the terminal (-). As a result, the voltage is delivered to a feedback resistance Rf. With this voltage, the general sum of the current values which are flowed between the terminal (-) and the earth point of a circuit is equal to the sum of the potential of the terminal (-). In other words, an analog signal of the level corresponding to the signals D1 and D2 each is delivered to the output terminal of the amplifier OP1. |
