Current monitoring for time division duplex power amplifier in a communication system

A current monitoring circuit for a time division duplex (TDD) power amplifier in a communication system, the current monitoring circuit comprising:

• a voltage measurement circuit configured to generate current equivalent voltage output signals;
• and
• a stabilizer circuit including,
• a switch including a first post coupled to an output of the voltage measurement circuit;
• a first resistor having a first side coupled to a second post of the switch:
• a capacitor coupled in series with the first resistor, the capacitor further coupled to ground;
• a first voltage supply coupled to control the switch synchronized with the first voltage supply by a TDD switching signal used to switch radio frequency (RF) transistors in the TDD power amplifier;
• a second resistor having a first side coupled to the second post of the switch and a second side coupled to the ground;
• a third resistor having a first side coupled to the second post of the switch;
• a second operational amplifier having a first input coupled to receive the current equivalent voltage signals output from the voltage measurement circuit, the second operational amplifier having a second input coupled the output of the second operational amplifier, the output of the second operational amplifier coupled to the first post of the switch;
• and
• a third operational amplifier having a first input coupled to a second side of the third resistor, the third operational amplifier having a second input coupled to an output of the third operation amplifier, the output of the third operational amplifier coupled to an analog-to-digital converter (ADC).

A method of operating a communication system, the method comprising:

• generating TDD switching signals having transmit time frames and receive time frames;
• controlling radio frequency (RF) transistors in a TDD power amplifier based on the TDD switching signals, wherein the TDD switching signals selectively turn on and off the RF transistors based on the transmit time frames and receive time frames;
• generating current equivalent voltage output signals from a voltage drop of a sense resistor in a direct current (DC) supply line coupled to the TDD power amplifier with a voltage measurement circuit;
• stabilizing the equivalent voltage output signal by selectively applying a stabilizer circuit that includes a capacitor in series with a resistor during a transmit frame in the TDD switching signals and disconnecting the stabilizer circuit during a receive frame of the TDD switching signals;
• converting the equivalent voltage output signal to a digital signal equivalent voltage output signal;
• reading the digital signal current equivalent voltage output signal off of a bus;
• and
• determining a current of the TDD power amplifier from the digital signal current equivalent voltage read off of the bus.