最完整的全差分运算放大器的设计
五、SPICE仿真
1． DC工作点与AC特性
首先我们在输入端为2.5V共模电压的情况下，进行直流工作点的分析，对某些MOS管进行修改和调整。手工计算和SPICE仿真的管子尺寸如表格1所示。
表格一、管子尺寸、工作电流与有效电压 IDS MOS 管（计算值）
80µm/2µm 200µAM1 M2 M17
M3 M4
M5 M6
M7 M8
M9 M10
M11 M12
M13 M14
M15 M16
M18
M19
M20
MB1 MB2 MB3
MB4
MB5 MB6
MB13
MB7 MB8
MB14
MB9
MB10
MB11
MB12
120µm/1µmµA60µm/1µmµA60µm/1µmµA100µm/1µmµA360µm/1µm 900µA160µm/1µmµA40µm/2µmµA80µm/1µmµA40µm/1µmµA40µm/1µmµA10µm/2µmµA2.5µm/1µmµA10µm/1µmµA10µm/1µmµA10µm/1µmµA5µm/1µmµA5µm/1µmµA1.25µm/1µm 25µAVeff
0.425V 0.3V 0.3V 0.3V 0.254V 0.3V 0.3V 0.425V 0.3V 0.3V 0.3V 0.290V 0.602V 0.30V 0.30V 0.30V 0.290V 0.290V 0.580V W/L（仿真）100µm/2µm120µm/1µm60µm/1µm60µm/1µm100µm/1µm300µm/1µm160µm/1µm40µm/2µm80µm/1µm40µm/1µm40µm/1µm10µm/2µm2.5µm/1µm10µm/1µm10µm/1µm10µm/1µmIDS 227µA 341µA 341µA 341µA 1000µA 1000µA 454µA 114µA 227µA 227µA 227µA 25µA 26.4µA 26µA 26µA 26µA Veff 0.621V 0.369V 0.282V 0.298V 0.340V 0.396V 0.385V 0.528V 0.368V 0.283V 0.297V 0.277V 0.854V 0.361V 0.382V 0.356V 0.274V 0.327V 0.797V 5µm/1µmµA 5µm/1µmµA 1µm/1µm 26µA
图7 压摆率测试电路图
图6 AC频响测试图