Power amplifier circuit with temperature compensating level shifter

A power amplifier circuit for amplifying a radio frequency (RF) signal into an amplified RF signal, the power amplifier circuit comprising:

• a first input to receive the RF signal;
• an output to provide the amplified RF signal;
• a coupler circuit coupled to the output to detect a level of the amplified RF signal;
• a second input to receive a control signal derived from the level;
• a power amplifier comprising a first transistor, the first transistor having a gate and a drain, the gate coupled to the first input, and the drain coupled to the output;
• and
• a level shifter coupled to the second input and the gate, the level shifter, responsive to the control signal, supplying a biasing voltage to the gate to set an amplification level of the first transistor, the level shifter minimizing temperature sensitivity of the biasing voltage, the level shifter comprising a temperature compensating circuit, the temperature compensating circuit comprising a VBE Multiplier.

A power amplifier circuit for amplifying a radio frequency (RF) signal into an amplified RF signal, the power amplifier circuit comprising:

• a first input to receive the RF signal;
• an output to provide the amplified RF signal;
• a coupler circuit coupled to the output to detect a level of the amplified RF signal;
• a second input to receive a control signal derived from the level;
• a power amplifier comprising a first transistor, the first transistor having a gate and a drain, the gate coupled to the first input, and the drain coupled to the output;
• and
• a level shifter coupled to the second input and the gate, the level shifter, responsive to the control signal, supplying a biasing voltage to the gate to set an amplification level of the first transistor, the level shifter comprising a feedback circuit and a temperature compensating circuit, the temperature compensating circuit comprising:
• a second transistor having a first terminal, a second terminal, and a third terminal, the first terminal coupled to the feedback circuit, the second terminal coupled to the feedback circuit and the gate of the first transistor of the power amplifier;
• a first resistive element having two ends, one end of the first resistive element coupled to the first terminal and the feedback circuit, and the other end of the first resistive element coupled to the third terminal;
• and
• a second resistive element having two ends, one end of the second resistive element coupled to the third terminal and the other end of the second resistive element coupled to the second terminal and the gate of the first transistor of the power amplifier, the level shifter minimizing temperature sensitivity of the biasing voltage.

A communication device comprising:

• an antenna;
• a receiver coupled to the antenna to receive a radio frequency (RF) input signal therefrom;
• a controller having a first input, a second input, a first output, and a second output, the first input coupled to the receiver to receive the RF input signal, the controller to format an RF output signal and couple the RF output signal to the first output, the controller, responsive to a presence of a level signal at the second input, generating a control signal and coupling the control signal to the second output;
• and
• a transmitter having a third input, a fourth input, a third output, and a fourth output, the third input coupled to the first output, the fourth input coupled to the second output, the third output coupled to the second input, the fourth output coupled to the antenna, the transmitter comprising a power amplifier coupled to the third input and the fourth output, a coupler coupled to the third output and the fourth output, and a level shifter coupled to the fourth input and the power amplifier, the power amplifier amplifying the RF output signal at the third input and providing an amplified RF output signal at the fourth output, the coupler coupling a level signal to the third output describing a level of the amplified RF output signal at the fourth output, and the level shifter, responsive to the control signal at the fourth input, supplying a temperature compensated biasing voltage to the power amplifier.