Differential Power Amplifier Bias Control via Transformer Midpoint
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Solution Overview
Problem
The gain dispersion of a power amplifier circuit with a differential amplifier circuit affects the symmetry of the circuit, necessitating an improvement that maintains symmetry while achieving appropriate gain dispersion.
Innovation Solution
A power amplifier circuit comprising a differential amplifier circuit, a transformer with a primary and secondary winding, and an adjustment circuit coupled to the midpoint of the primary winding. The adjustment circuit adjusts the bias current or voltage based on a supply voltage controlled by the envelope of the radio-frequency signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an adjustment circuit is added to control gain dispersion, then gain dispersion characteristic is improved, but circuit complexity increases and symmetry of differential amplifier circuit is affected
Solution Approach 1:
The patent introduces a transformer as an intermediary component between the differential amplifier circuit and the adjustment circuit. The transformer's primary winding is connected to the supply voltage and the adjustment circuit, while the secondary winding provides the amplified signal. This intermediary structure allows the adjustment circuit to control gain dispersion without directly interfering with the symmetry of the differential amplifier circuit, as the transformer isolates the adjustment actions from the differential pair.
Solution Approach 2:
The patent segments the circuit into distinct functional blocks: the differential amplifier circuit for signal amplification, the transformer for voltage transformation and isolation, and the adjustment circuit for gain dispersion control. By separating the gain control function into a standalone adjustment circuit that operates through the transformer, the patent avoids complicating the internal structure of the differential amplifier circuit while still achieving effective gain dispersion management.
2Reliability
If bias current is adjusted to improve gain dispersion, then gain control is improved, but symmetry of differential amplifier circuit is affected
Solution Approach 1:
The transformer serves as a mediator that allows bias current adjustment to be applied to the differential amplifier circuit without directly disrupting its symmetry. The adjustment circuit modifies the supply voltage through the transformer's primary winding, and the transformed signal is then applied to the differential pair. This indirect adjustment mechanism maintains the symmetrical structure of the differential amplifier while achieving the desired gain control.
Solution Approach 2:
The patent changes the supply voltage parameter dynamically through the adjustment circuit to control gain dispersion. By varying the supply voltage in response to the envelope of the RF signal, the circuit achieves adaptive gain control. The transformer ensures that these parameter changes are applied in a manner that preserves the symmetrical operation of the differential amplifier circuit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves appropriate gain dispersion without affecting the symmetry of the differential amplifier circuit, ensuring proper operation even with fluctuating radio-frequency signal amplitudes.
Implementation Method 1
The transformer includes a primary winding and a secondary winding
Data Source
AI summary
A power amplifier circuit includes a differential amplifier circuit configured to amplify a radio-frequency signal, a transformer disposed on an output side with respect to the differential amplifier circuit and including a primary winding and a secondary winding, and a dispersion circuit coupled to a midpoint of the primary winding of the transformer and configured to operate as an adjustment circuit. The dispersion circuit is configured to adjust, based on a supply voltage controlled in accordance with the envelope of the radio-frequency signal, a bias (bias current or bias voltage) to be supplied to the differential amplifier circuit.