The adjoint transformation usage for correction of the attenuation of the low-pass biquad in the current mode

Abstract

The second order Sallen-Key low-pass filter structures (so called biquads) in the voltage and current mode have one common disadvantage, it is a decreasing of the attenuation in the stopband. This fact is caused by losses of the amplification factor of active elements at high frequencies. Some solutions of this problem had been already published for circuits working in the voltage mode, but this problem was not satisfactorily solved for circuits working in the current mode. Therefore, this article presents one of the possible solutions of this problem for circuits working in the current mode.