Low-power undervoltage lockout circuits

A communication device comprising:

• receive circuitry;
• transmit circuitry;
• and
• antenna switching circuitry, which is configured to transmit radio frequency (RF) signals between antennas and the receive circuitry and/or between the antennas and the transmit circuitry, wherein at least one undervoltage lockout (UVLO) circuit, which is configured to monitor an input voltage and disable circuitry when the voltage is too low, is included in at least one of the transmit circuitry, the receive circuitry, and the antenna switching circuitry, wherein:
• the UVLO circuit comprises a first branch and a second branch;
• the first branch comprises a first transistor and a feedback transistor, wherein a source electrode of the first transistor is electrically coupled to an input voltage, and a drain electrode and a gate electrode of the first transistor are electrically coupled to a source electrode of the feedback transistor;
• the second branch comprises a second transistor, wherein a source electrode of the second transistor is electrically coupled to the input voltage, a drain electrode of the second transistor is electrically coupled to a gate electrode of the feedback transistor, and a gate electrode of the second transistor is electrically coupled to the gate electrode of the first transistor;
• and
• in response to the input voltage being below a threshold value, the feedback transistor is turned off, and in response to the input voltage being above the threshold value, the feedback transistor is turned on and a voltage at the gate electrode of the feedback transistor becomes a constant voltage value.