A filter network, comprising: an amplifier having an input and an output; a passive filter coupled to the output of the amplifier and configured to add at least one pole to a transfer function of the filter network; a voltage buffer (212, 400C) having an input coupled to the passive filter and an output; a resistor coupled between the output of the voltage buffer and the input of the amplifier; a capacitor coupled between the output of the amplifier and the input of the amplifier; and a circuit package housing at least the amplifier, the passive filter, and the voltage buffer (212, 400C); characterized in that the voltage buffer (212, 400C) comprises: a first current source connected between a supply voltage (Vs) and a first node: a first transistor, having a gate terminal connected to the input of the voltage buffer, a drain terminal connected to the first node, and a source terminal connected to the output of the voltage buffer; a second transistor, having a gate terminal connected to a second node, a drain terminal connected to the output of the voltage buffer, and a source terminal connected to a reference potential; a third transistor, having a gate terminal operable to receive a bias voltage, a drain terminal connected to the second node, and a source terminal connected to the first node; and a second current source connected between the second node and the reference potential. an amplifier having an input and an output; a passive filter coupled to the output of the amplifier and configured to add at least one pole to a transfer function of the filter network; a voltage buffer (212, 400C) having an input coupled to the passive filter and an output; a resistor coupled between the output of the voltage buffer and the input of the amplifier; a capacitor coupled between the output of the amplifier and the input of the amplifier; and a circuit package housing at least the amplifier, the passive filter, and the voltage buffer (212, 400C); characterized in that the voltage buffer (212, 400C) comprises: a first current source connected between a supply voltage (Vs) and a first node: a first transistor, having a gate terminal connected to the input of the voltage buffer, a drain terminal connected to the first node, and a source terminal connected to the output of the voltage buffer; a second transistor, having a gate terminal connected to a second node, a drain terminal connected to the output of the voltage buffer, and a source terminal connected to a reference potential; a third transistor, having a gate terminal operable to receive a bias voltage, a drain terminal connected to the second node, and a source terminal connected to the first node; and a second current source connected between the second node and the reference potential. a first transistor, having a gate terminal connected to the input of the voltage buffer, a drain terminal connected to the first node, and a source terminal connected to the output of the voltage buffer; a second transistor, having a gate terminal connected to a second node, a drain terminal connected to the output of the voltage buffer, and a source terminal connected to a reference potential; a third transistor, having a gate terminal operable to receive a bias voltage, a drain terminal connected to the second node, and a source terminal connected to the first node; and a second current source connected between the second node and the reference potential.