A device comprising: a first multiple-output transconductance amplifier (15, 16) that comprises a non-inverting input, an inverting input, an inverted output, a first non-inverted output, and a second non-inverted output, the outputs being current outputs, wherein the first non-inverted output is connected to the inverting input, and the non-inverting input is connected to a first input voltage terminal; a second multiple-output transconductance amplifier (29, 30) that comprises a non-inverting input, an inverting input, a first non-inverted output, a second non-inverted output, and an inverted output, the outputs being current outputs, wherein the first non-inverted output is connected to the inverting input, and the non-inverting input is connected to a second input voltage terminal; a first resistor, wherein a first end of the first resistor is connected to the inverting input of the first multiple-output transconductance amplifier, and a second end of the first resistor is connected to the inverting input of the second multiple-output transconductance amplifier; a first node connected to both the second non-inverted output of the first multiple-output transconductance amplifier (15, 16) and the inverted output of the second multiple-output transconductance amplifier; a second node connected to both the inverted output of the first multiple-output transconductance amplifier and the second non-inverted output of the second multiple-output transconductance amplifier; a second resistor (42, 112, 132), wherein a first end of the second resistor is connected to the first node; a third resistor (80, 94, 134), wherein a first end of the third resistor is connected to the second node; a first output terminal downstream of the first node; and a second output terminal downstream of the second node. a first multiple-output transconductance amplifier (15, 16) that comprises a non-inverting input, an inverting input, an inverted output, a first non-inverted output, and a second non-inverted output, the outputs being current outputs, wherein the first non-inverted output is connected to the inverting input, and the non-inverting input is connected to a first input voltage terminal; a second multiple-output transconductance amplifier (29, 30) that comprises a non-inverting input, an inverting input, a first non-inverted output, a second non-inverted output, and an inverted output, the outputs being current outputs, wherein the first non-inverted output is connected to the inverting input, and the non-inverting input is connected to a second input voltage terminal; a first resistor, wherein a first end of the first resistor is connected to the inverting input of the first multiple-output transconductance amplifier, and a second end of the first resistor is connected to the inverting input of the second multiple-output transconductance amplifier; a first node connected to both the second non-inverted output of the first multiple-output transconductance amplifier (15, 16) and the inverted output of the second multiple-output transconductance amplifier; a second node connected to both the inverted output of the first multiple-output transconductance amplifier and the second non-inverted output of the second multiple-output transconductance amplifier; a second resistor (42, 112, 132), wherein a first end of the second resistor is connected to the first node; a third resistor (80, 94, 134), wherein a first end of the third resistor is connected to the second node; a first output terminal downstream of the first node; and a second output terminal downstream of the second node.