A Generic Current Mode Design for Multifunction Grounded Capacitor Filters Employing Log-Domain Technique

Table 2

𝑇𝑎𝑏𝑙𝑒 demonstrating that the four MFF configurations presented in the paper are the only stable ones.

Mode of integrators^*		Type of feedback^#		HP transfer function	Stability status^~
I1	I2	F1	F2
NI	NI	+	+	𝑠^2𝑠^2−(𝑠/𝜏1)−1/𝜏1𝜏2	U
NI	I	+	−
I	NI	−	−
I	I	−	+
NI	NI	+	−	𝑠^2𝑠^2−(𝑠/𝜏1)+1/𝜏1𝜏2	U
NI	I	+	+
I	NI	−	+
I	I	−	−
NI	NI	−	+	𝑠^2𝑠^2+(𝑠/𝜏1)−1/𝜏1𝜏2	U
NI	I	−	−
I	NI	+	−
I	I	+	+
NI	NI	−	−	𝑠^2𝑠^2+(𝑠/𝜏1)+1/𝜏1𝜏2	S
NI	I	−	+
I	NI	+	+
I	I	+	−

*I₁: First integrator after summation, I₁: Second integrator after summation, NI: Noninverting, I: Inverting.
^#F₁: Feedback from first integrator, F₂: Feedback from second integrator.
^~U: Unstable, S: Stable.