说明：  设计一个完整的连续可调直流稳压电源电路，其主要技术指标要求：输出电压可调：Uo=+3V～+12V；最大输出电流：Iomax=800mA；输出电压变化量：ΔUo≤15mV；稳压系数：SV≤0.003。
(Design a complete the continuous adjustable DC power supply circuit, its main technical indicators requirements: (1) the output voltage adjustable: the Uo =+3V ~+12V ② maximum output current: Iomax = 800mA (3) output voltage changes: ΔUo ≤ 15mV ④ regulator factor: SV ≤ 0.003.)