An apparatus comprising: a current to voltage, I-V, filter configured to receive a respective input current signal at a first and second input terminal of an input port and to generate a respective filtered output voltage signal at a first and second output terminal of an output port based on a feedback transconductance, the respective input current signal comprising an input DC current; and a feedback circuit connected between the output port and the input port , the feedback circuit configured to provide the feedback transconductance for the I-V filter, the feedback circuit comprising: first and second transistors (T1a, T1c) having drain terminals connected to the first input terminal of the input port , source terminals connected to a ground signal, and first and second gate terminals connected to the second and first output terminals of the output port , respectively, third and fourth transistors (T1b, T1d) having drain terminals connected to the second input terminal of the input port , source terminals connected to the ground signal, and third and fourth gate terminals connected to the second and first output terminals of the output port , respectively, a first capacitor connected between the first input terminal of the input port and the first output terminal of the output port , and a second capacitor connected between the second input terminal of the input port and the second output terminal of the output port . a current to voltage, I-V, filter configured to receive a respective input current signal at a first and second input terminal of an input port and to generate a respective filtered output voltage signal at a first and second output terminal of an output port based on a feedback transconductance, the respective input current signal comprising an input DC current; and a feedback circuit connected between the output port and the input port , the feedback circuit configured to provide the feedback transconductance for the I-V filter, the feedback circuit comprising: first and second transistors (T1a, T1c) having drain terminals connected to the first input terminal of the input port , source terminals connected to a ground signal, and first and second gate terminals connected to the second and first output terminals of the output port , respectively, third and fourth transistors (T1b, T1d) having drain terminals connected to the second input terminal of the input port , source terminals connected to the ground signal, and third and fourth gate terminals connected to the second and first output terminals of the output port , respectively, a first capacitor connected between the first input terminal of the input port and the first output terminal of the output port , and a second capacitor connected between the second input terminal of the input port and the second output terminal of the output port . first and second transistors (T1a, T1c) having drain terminals connected to the first input terminal of the input port , source terminals connected to a ground signal, and first and second gate terminals connected to the second and first output terminals of the output port , respectively, third and fourth transistors (T1b, T1d) having drain terminals connected to the second input terminal of the input port , source terminals connected to the ground signal, and third and fourth gate terminals connected to the second and first output terminals of the output port , respectively, a first capacitor connected between the first input terminal of the input port and the first output terminal of the output port , and a second capacitor connected between the second input terminal of the input port and the second output terminal of the output port . <EOS>