Academy & Industry Research Collaboration Center (AIRCC)

Volume 10, Number 10, July 2020

Derivation of Loop Gain and Stability Test for Low-pass Tow-Thomas Biquad Filter


MinhTri Tran, Anna Kuwana and Haruo Kobayashi, Gunma University, Japan


Proposed derivation and measurement of self-loop function for a low-pass Tow Thomas biquadratic filter are introduced. The self-loop function of this filter is derived and analyzed based on the widened superposition principle. The alternating current conservation technique is proposed to measure the self-loop function. Research results show that the selected passive components (resistors, capacitors) of the frequency compensation of Miller’s capacitors in the operational amplifier and the Tow Thomas filter can cause a damped oscillation noise when the stable conditions for the transfer functions of these networks are not satisfied.


Superposition, Self-loop Function, Stability Test, Tow-Thomas Biquadratic Filter, Voltage Injection.