A 356-μW, 433-MHz, Rail-to-Rail Voltage Amplifier with Carrier Sensing Function for Wireless Sensor Networks

We describe a low-power voltage amplifier that is suitable for RF (radio frequency) receivers in a WSN (wireless sensor network). Since a sensor node has a strict energy budget in a WSN, it often enters itself into a standby mode when no communication is required, and hence a standby power have to be suppressed as well as an active power in order to maximize a lifetime of a WSN. For this sake, it is effective to reduce an RF block’s power in a sensor node because it is the major power-consuming block. We propose a simple rail-to-rail voltage amplifier with lowstandby-power and low-active-power capabilities that is suitable to a subsequent digital interface. The target frequency is set to 433 MHz, and the voltage gain achieves 26 dB. The standby and active powers are 24 nW and 356 μW, which are lower than the conventional inverter-type voltage amplifier by 86% and 46%, respectively. The proposed amplifier features a carrier sensing function in addition to the low-power operation since it has a minimum input amplitude to be amplified. By using this function, we can set a carrier sensing level as a threshold level, which is important to avoid collisions and interferences in a WSN that cause needless communications. Index Terms — Wireless sensor network, voltage amplifier, carrier sense, on-off keying.