A voltage-to-current converter includes a first transistor having a drain coupled to a first node, a second transistor having a drain coupled to the first node, an operational amplifier having a first input terminal configured to receive a reference voltage and a second input terminal coupled to a source of the first transistor or a source of the second transistor, a control circuit having an input terminal coupled to an output terminal of the operational amplifier, a first output terminal coupled to a gate of the first transistor, and a second output terminal coupled to a gate of the second transistor, a first resistor coupled between the source of the first transistor and a ground, and a second resistor coupled between the source of the second transistor and the ground. An output current of the voltage-to-current converter is generated from the first node.