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.