The invention relates to the field of antibiotic compositions, both inside and outside the medical field. A buildup electrode of a lower layer has a tapered shape in a peripheral portion and the common electrode of an upper layer is formed so as to cover the buildup electrode. The open gap may be formed by supporting struts that connect the catheter to the catheter head. The comparator compares an input voltage and an output voltage and outputs a control signal to the bias current source according to the compared result to control a bias current outputted by the bias current source to enhance the slew rate of the output buffer.