Doherty Amplifier Bias Path Resistor for Peak Stage Stability
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Solution Overview
Problem
In Doherty amplifiers formed on a semiconductor substrate, the power supply terminal experiences a finite inductance, leading to a low impedance and AC amplitude due to signal leakage, which can cause the peak amplifier to malfunction when the bias points of the carrier and peak amplifiers differ, resulting in the peak amplifier being driven by leaking signals.
Innovation Solution
Incorporating a first resistor in series with the power supply path to the peak amplifier to attenuate the leaking radio-frequency signal, reducing the likelihood of the peak amplifier malfunctioning, and using a capacitor to further attenuate the signal and achieve impedance matching between amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bias point of the first-stage amplifier in the peak amplifier is lowered to control its operation, then the efficiency of the Doherty amplifier is improved, but the leaking signal drives the posterior amplifier through the inductor causing malfunction
Solution Approach 1:
A resistor is inserted in series with the inductor in the power supply path to the peak amplifier. This resistor acts as an intermediary element that blocks the leaking radio-frequency signal from driving the posterior amplifier while still allowing the low bias current to flow, thus preventing malfunction without sacrificing efficiency.
Solution Approach 2:
The invention changes the electrical parameters of the power supply path by adding a resistor with specific resistance value. This modifies the impedance characteristics to attenuate the leaking signal at radio-frequency while maintaining the desired DC bias conditions, resolving the contradiction between efficiency and reliability.
2Reliability
If a resistor is inserted in series into the power supply path to the second amplifier, then the leaking signal is attenuated reducing malfunction likelihood, but the device complexity increases
Solution Approach 1:
The power supply path is segmented by inserting a resistor in series with the inductor. This divides the previously single-component power supply path into two separate elements, allowing independent optimization of each component's function - the inductor for power delivery and the resistor for signal attenuation.
Solution Approach 2:
A simple resistor, which is a low-cost and straightforward component, is added to the circuit. This inexpensive element effectively blocks the harmful leaking signal without requiring complex active components or sophisticated circuitry, thus minimizing the increase in device complexity.
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 resistor and capacitor configuration effectively reduce the impact of leaking signals on the peak amplifier, preventing malfunction and ensuring proper operation by attenuating the radio-frequency signal and maintaining impedance matching, thereby enhancing the reliability of the Doherty amplifier.
Implementation Method 1
a first resistor that is inserted in series into a power supply path to the second amplifier
Implementation Method 2
the power supply terminal on the semiconductor substrate is connected with a finite inductance interposed
Data Source
AI summary
A Doherty amplifier includes: a carrier amplifier that is formed on a semiconductor substrate and that includes amplifiers in one or more stages including a first amplifier in one stage to which a first bias current is inputted; a peak amplifier that is formed on the semiconductor substrate and that includes amplifiers in two or more stages including a second amplifier to which a second bias current smaller than the first bias current is inputted; and a first resistor that is inserted in series into a power supply path to the second amplifier.