如图2-90所示为实现DAC的一种电路。电路输出电压满足[tex=16.071x1.429]0AVzNl1u170Oqdct9IoSp+qV+1N7rwY4g/+SOK0blqxe+bmRoEqM4tQaPlbAB3A570AvJ/zIwk6oluVaO7T/nUusjE5fojwrNChvOAL1dw+iftnC67W+l/ImecZnVGtv[/tex],试求[tex=3.357x1.286]a01AGD5lVy1o87QoT3pVgQ==[/tex]应满足的关系，并求图2-56所示电路的输出电压。[img=411x234]17d2160e27e112a.png[/img]