一、有一個理想運算放大器(Operational Amplifier)電路如圖一所示,此電路有 3 個輸入電壓訊號,分別為:。電路中 = 80 kΩ,R1 = 40 kΩ, R2 = 10 kΩ ,R3 =20 kΩ ,R4 = 10 kΩ ,R5 = 20 kΩ 。請計算 = ?