Stacked Transconducting Cell Amplifier for Current-Mode RF Power Combining
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Solution Overview
Problem
Conventional high-frequency millimeter-wave amplifiers face limitations in output power and reliability due to voltage handling issues and large layout size requirements, particularly when using stacked device approaches in voltage mode combining techniques.
Innovation Solution
The design employs stacked transconducting cells in current mode combining, where a direct current (DC) supply current is shared cascode and alternating current (AC) RF input and output currents are connected in cascade, with a single-input single-output matching network for both input and output, reducing gate/base resistive losses and dependency on gate capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If stacked device approaches with voltage mode combining techniques are used, then output power can be increased, but layout size becomes large and reliability concerns arise
Solution Approach 1:
The patent merges multiple transconducting cells in a stacked configuration where they share a common DC bias current path while their AC signal paths are combined through current mode combining. This allows the amplifier to achieve high output power through current summation rather than voltage stacking, significantly reducing the required layout area while maintaining reliability
Solution Approach 2:
The invention changes the combining mode from voltage mode to current mode. In current mode combining, the AC output currents from stacked transconducting cells are summed directly at the output node, whereas conventional voltage mode requires separate voltage paths and larger layout area. This parameter change enables compact design with improved power density
2Power
If stacked device approaches with voltage mode combining techniques are used, then output power can be increased, but reliability concerns arise due to voltage swing issues
Solution Approach 1:
The patent changes the operating mode from voltage mode to current mode, fundamentally altering how signals are combined. In current mode, each transconducting cell operates with reduced voltage swings since they share a common bias current, eliminating the voltage breakdown reliability issues that plague conventional stacked voltage mode amplifiers. The output is taken as the sum of collector or drain currents rather than voltage swings
Solution Approach 2:
The amplifier is segmented into multiple transconducting cells that each handle a portion of the total current. By dividing the total output current among multiple parallel-connected transconducting devices, each device operates at lower stress levels, improving individual device reliability while achieving high total output power through current summation
3Power
If conventional stacked device approaches are used, then power supply voltage can be distributed, but device complexity and layout size increase
Solution Approach 1:
The stacked transconducting cells serve multiple functions simultaneously: they distribute the power supply voltage across multiple devices to reduce individual device voltage stress, they provide current mode combining for high output power, and they maintain a compact layout through shared bias current paths. This multi-functionality reduces overall device complexity despite the stacked configuration
Data Source
AI summary
An amplifier with stacked transconducting cells in “current mode combining” is disclosed herein. In one or more embodiments, a method for operation of a high-voltage signal amplifier comprises inputting, into each transconducting cell of a plurality of transconducting cells, a direct current (DC) supply current (Idc), an alternating current (AC) radio frequency (RF) input current (IRF_IN), and an RF input signal (RFIN). The method further comprises outputting, by each of the transconducting cells of the plurality of transconducting cells, the DC supply current (Idc) and an AC RF output current (IRF_OUT). In one or more embodiments, the transconducting cells are connected together in cascode for the DC supply current, and are connected together in cascade for the AC RF input and output currents.