## 5 Conclusions  
The die microphotograph of the fabricated LNA and the corresponding transistors and inductor sizes are shown in Figure 13, with the die area including pads of 0.75 \(\times\) 0.69 mm\({}^{2}\). The target frequencies of the proposed triple-band LNAs were 2.5, 3.5, and 5.2 GHz, which can be used in TD-LTE, mid-band 5G, LTE-U, and WLAN technology. A triple-band LNA with a switched resonator concept was fabricated using TSMC 0.18-\(\upmu\)m CMOS technology, and a considerable die area reduction was achieved. Furthermore, an additional substrate resistance \(R_{B}\) diminished the output noise power density of the MOS device, and a 0.71/0.67/0.64-dB decrease in the noise figure was attained at 2.5/3.5/5.2 GHz by using the triple-band LNA without additional chip area, dc power, and CMOS process steps. The frequency range for each band are 2.3-2.7, 3.4-3.8, and 5.1-5.9 GHz, including TD-LTE Band 40-41, Band 42-43, mid-band 5G, and the unlicensed 5-GHz band operation. The measured 10 dB return loss can be achieved to fulfil triple-band operation with moderate gain around 12 dB, and 2.2-2.7 dB noise figure. The measurement result agrees well with the simulation result. **Author Contributions:** The study was performed by authors as follows: Conceptualization: [PERSON] and [PERSON]; methodology: [PERSON] and [PERSON]; validation: [PERSON]; formal analysis: [PERSON]-[PERSON] and [PERSON]; investigation: [PERSON] and [PERSON]; writing--original draft preparation: [PERSON] and [PERSON]; writing--review and editing: [PERSON]; visualization: [PERSON] and [PERSON]; supervision: [PERSON], [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Acknowledgments: This work was supported by the National Science Council of Taiwan, Republic of China, under contract NSC96-2752-E009-003-PAE. The authors thank the National Chip Implementation Center (CIC), Taiwan, for their help in chip fabrication. Conflicts of Interest: The authors declare no conflict of interest. References  
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