Doherty Peak Bias Circuit With Predetermined Current Feed
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Solution Overview
Problem
The Doherty amplifier circuit experiences signal distortion, increased adjacent channel leakage power, and elevated error vector magnitude due to the delay in the response of the bias circuit in the peak amplifier, which is caused by the small current flowing through the bias circuit.
Innovation Solution
A power amplification module is designed with a Doherty amplifier circuit that includes a carrier amplifier and a peak amplifier, where the peak bias circuit is enhanced with a current output circuit to improve the response delay of the bias circuit. This is achieved by using a first transistor with its collector or drain connected to a reference potential, supplying bias to the peak amplifier from its emitter or source, and being electrically connected to a current output circuit that provides a predetermined current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the peak amplifier operates in Class C with low base bias current to improve efficiency, then power efficiency is improved, but the bias circuit response delay increases causing signal distortion and adjacent channel leakage
Solution Approach 1:
The patent applies preliminary action by providing a predetermined current to the peak bias circuit in advance, before the peak amplifier needs to respond to signal changes. This predetermined current is supplied through a current output circuit that is always active, ensuring the bias circuit is ready to respond immediately when the peak amplifier needs to operate, thus eliminating response delay while maintaining the efficiency benefits of Class C operation.
2Loss of energy
If the peak amplifier operates in Class C with low base bias current, then power efficiency is improved, but the bias circuit cannot follow the input signal changes causing distortion
Solution Approach 1:
The current output circuit provides a predetermined current to the peak bias circuit in advance, ensuring the bias circuit is always ready to respond quickly to input signal changes. This preliminary current supply maintains the bias circuit's responsiveness without requiring continuous high current that would reduce power efficiency.
3Power
If the peak amplifier starts to operate at high power levels, then output power is increased, but the gain and phase characteristics change causing error vector amplitude increase
Solution Approach 1:
The patent employs feedback by using the output signal of the carrier amplifier as a reference to control the peak amplifier's operation. The current output circuit receives control signals based on the carrier amplifier's output, allowing the peak amplifier to be activated at the optimal moment and maintain stable gain and phase characteristics throughout the signal cycle, thereby reducing error vector amplitude.
Data Source
AI summary
A power amplification module includes a carrier amplifier circuit; a carrier bias circuit that supplies a bias to the carrier amplifier circuit; a peak amplifier circuit; and a peak bias circuit that includes a first transistor having a collector or a drain connected to a reference potential and that supplies a bias to the peak amplifier circuit from an emitter or a source of the first transistor. The peak bias circuit is electrically connected to a current output circuit that outputs a predetermined current from the emitter or the source of the first transistor.