Cascode Amplifier Turn-Off Using Drain-Voltage Feedback
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Solution Overview
Problem
Modern power supply designs experience significant power loss due to switching losses when transitioning between ON and OFF states, primarily caused by voltage changes while current is flowing, which is not efficiently managed by existing technologies.
Innovation Solution
An apparatus comprising a cascode amplifier with a common-gate transistor and a common-source transistor, coupled with a feedback circuit and a bias circuit, that senses the rising drain-voltage and adjusts the gate-voltage to maintain the common-gate transistor in an active state until a second gate-voltage is applied, allowing for faster switching to an OFF state, thereby reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the common-source transistor is switched to OFF state, then the drain-voltage increases, but the switching loss increases due to voltage rising while current is flowing
Solution Approach 1:
The feedback circuit detects the drain-voltage rise in advance and triggers the bias circuit to adjust the gate-voltage of the common-gate transistor before the switching transition is complete. This preliminary action prepares the transistor for faster switching while controlling the voltage-current overlap, thereby reducing switching losses.
Solution Approach 2:
The feedback circuit continuously monitors the drain-voltage and provides real-time information to the bias circuit. Based on this feedback, the bias circuit dynamically adjusts the gate-voltage to optimize the switching transition, enabling faster switching speed while minimizing the energy loss during the transition period.
2Reliability
If the gate-voltage is adjusted to maintain the common-gate transistor in active state, then the switching transition is optimized, but the device complexity increases due to feedback and bias circuits
Solution Approach 1:
The feedback circuit and bias circuit act as intermediary components that mediate between the switching signal and the common-gate transistor. The feedback circuit intermediates by detecting voltage changes, and the bias circuit intermediates by providing adjusted gate-voltage, thereby improving switching control reliability without requiring fundamental changes to the basic transistor structure.
Data Source
AI summary
An apparatus for turning off a cascode amplifier having a common-gate transistor and a common-source transistor is disclosed that includes the cascode amplifier, a feedback circuit, and a bias circuit. The feedback circuit is configured to receive a drain-voltage from the drain of the common-source transistor when the common-source transistor is switched to a first OFF state and produce a first feedback signal. The drain-voltage is equal to a source voltage of the common-gate transistor and the drain-voltage increases in response to switching the common-source transistor to the first OFF state. The bias circuit is configured to receive the first feedback signal and produce a bias-voltage. A first gate-voltage is produced from the bias-voltage. The cascode amplifier is configured to receive the first gate-voltage and a second gate-voltage. The common-gate transistor is configured to switch to a second OFF state in response to receiving the second gate-voltage.