设计并实现了数控变速调焦控制电路，该电路基于双极性三极管(PNP型和 NPN型)使之工作在射极输出器状态，对电机进行驱动。 FPGA接收上位机的控制信息，对电机转动进行高精度控制； DA数模转换器产生可，调模拟电压，调节电机的转速；模拟减法器产生 PNP型和 NPN型三极管的基极控制电压，保证电机正反转转速一致。仿真和实验表明，该电路工作稳定，结构简单，无需继电器，减小了体积，提高了稳定性，有利于产品的小型化，可广泛用于电动镜头内电机手动调焦和自动聚焦等场合，提高了调焦精度。

A numerical control focusing circuit with variable speed is designed and implemented. Based on bi.polar transistors such as PNP and NPN, the circuit is in the operation state of an emitter follower to drive the motor.The control information from upper computer is received by FPGA to control the motor accurately. The rotatingspeed of the motor can be adjusted through adjusting analog voltage generated by DA converter. The rotating speedof the motor is kept consistent by the base control voltage of PNP and NPN generated by an analog subtracter. Simu.lation and experimental results show that the circuit is in stable operation state, has simple structure without a relay,low volume and good stability, which can be used in focusing motors of lens widely.