3）求过程传递函数：微分方程组中消去中间变量?q2,?q3,?q12得：
?h1?h1??h2d?h1??q???C (6)1?1RRdtd?h2R12?212得： ?h?RC?(?1)?h2，再消去?h1有：?1122dtR3??h1??h2??h2?Cd?h2 (7)2?R3dt?R12d2?h2C1R12C2R12d?h2R2?R12?R3C1C2R12?(C??C?)??h2??q1 122dtR3R2dtR2R3对上式进行拉氏变换得：
G0?s??H2?s?Q1?s??1R?R12?R3CRCRC1C2R12s2?(C1?112?C2?212)s?2R3R2R2R3