Current steering biasing for power control in cascode-based power amplifier stage of radar applications for improved reliability

A power amplifier stage, comprising:

• a plurality of amplifier branch circuits, each amplifier branch circuit comprising:
• a corresponding one of a plurality of first cascode transistors having current terminals coupled between an output node and a corresponding one of a plurality of intermediate nodes, and having a control terminal receiving a corresponding one of a plurality of first activation signals;
• a corresponding one of a plurality of source transistors having current terminals coupled between a supply reference node and a corresponding one of the plurality of intermediate nodes, and having a control terminal receiving an input signal;
• and
• a corresponding one of a plurality of replica cascode transistors having current terminals coupled between a power supply node and the corresponding one of the plurality of intermediate nodes, and having a control terminal receiving a corresponding one of a plurality of complementary activation signals;
• and
• wherein a power output level of the power amplifier stage is controlled by asserting a selected number of the plurality of first activation signals and corresponding ones of the plurality of complementary activation signals for activating a selected number of the plurality of amplifier branch circuits;
• and
• wherein:
• activation of the plurality of first cascode transistors and deactivation of the plurality of replica cascode transistors produces an amplified input signal at the output node;
• and
• activation of the plurality of replica cascode transistors and deactivation of the plurality of first cascode transistors produces no power gain at the output node with respect to the input signal.

A transmitter chain of a radar system, comprising:

• a power amplifier stage comprising a plurality of amplifier branch circuits, where each of the plurality of amplifier branch circuits comprises:
• a first cascode device having current terminals coupled between an output node and an intermediate node, and having a control terminal receiving a corresponding one of a plurality of first activation signals;
• a source device having current terminals coupled between a supply reference node and the intermediate node, and having a control terminal receiving an input signal;
• and
• a replica cascode device having current terminals coupled between a power supply node and the intermediate node, and having a control terminal receiving a corresponding one of a plurality of complementary activation signals;
• and
• an output power controller that asserts a selected number of the plurality of first activation signals and corresponding ones of the plurality of complementary activation signals for activating a selected number of the plurality of amplifier branch circuits;
• wherein:
• switching current between the first cascode device and the replica cascode device reduces current level changes and overall current from a power supply of the power amplifier stage and
• deactivating the first cascode device and activating the replica cascode device results in no power gain for the input signal at the output node.