General model for delayed feedback and its application to transimpedance amplifier's bandwidth optimization

Delays in real systems can be of two types: i) intrinsic delays-due to the physical principles of operation of each electronic device; ii) designed delays-due to extra circuits used to add the desired delay. Previous work established the possibility of achieving bandwidth improvements using small delays inside the feedback loop of feedback amplifiers. The modeling approach followed on these contributions used only one designed delay element. The bandwidth reduction effect due to intrinsic delays was not considered on these contributions. This paper extends the concept to the general case of feedback amplifiers that incorporates delays of both types. An experimental demonstration using a simple 0.35 mu m BiCMOS transimpedance amplifier further confirms the proposed model.