Doherty Amplifier Resonance Layout for Bonding Wire Inductance
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Solution Overview
Problem
Doherty amplifiers face challenges in achieving wide-band and high-efficiency characteristics due to frequency deviations and unbalanced operations caused by inductance of bonding wires, particularly when the synthesized point is located at a pad of a peak amplifier or an end of a wire pad on a resin substrate.
Innovation Solution
A Doherty amplifier configuration where a capacitance value of a capacitor is selected to resonate with the inductance of a bonding wire, shifting the synthesized point and maintaining frequency characteristics, thereby achieving high-efficiency and wide-band performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bonding wires are used to connect transistor chips to circuits on resin substrate, then cost is reduced and manufacturing is simplified, but frequency characteristics degrade due to inductance of bonding wires
Solution Approach 1:
The patent converts the harmful inductance effect of bonding wires into a beneficial resonance effect by intentionally designing the bonding wire length to resonate at the operating frequency. This transforms the previously problematic inductance into a useful impedance transformation mechanism that actually improves frequency characteristics while maintaining the cost benefits of bonding wire connections
Solution Approach 2:
The patent changes the parameter of bonding wire length from being an unwanted parasitic element to a controlled design parameter. By specifically setting the bonding wire length to satisfy resonance conditions at the operating frequency, the inductance is transformed into a beneficial impedance transformation effect that improves frequency characteristics
2Device complexity
If synthesized point is located at pad of peak amplifier, then circuit layout is simplified, but unbalance operation occurs due to non-uniform load impedance
Solution Approach 1:
The patent introduces a ground wire as an intermediary element between the peak amplifier pad and ground. This ground wire, with specifically controlled length, acts as an impedance transformation element that compensates for the non-uniform load impedance caused by the pad geometry, thereby restoring balance to the operation while maintaining the simplified layout
3Reliability
If conventional matching circuit is used from transistors to synthesized point, then impedance matching is achieved, but bandwidth is limited due to frequency characteristics of matching circuit
Solution Approach 1:
The patent extracts and eliminates the conventional matching circuit from the design. Instead of using traditional matching components, the invention utilizes the inherent inductance of bonding wires and ground wires, combined with resonance conditions, to achieve impedance matching. This removal of conventional matching circuits eliminates their frequency limitations and enables wider bandwidth operation
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 resonance between the capacitor and bonding wire ensures stable frequency characteristics, enhancing the amplifier's efficiency and bandwidth, even with bonding wires connecting transistor chips to circuits on a resin substrate, resulting in improved output power and gain.
Implementation Method 1
a capacitance value of the first capacitor is selected so as to cause resonance with inductance of the second bonding wire
Data Source
AI summary
A first transistor chip (3) includes a first drain pad (5). A second transistor chip (4) includes a second drain pad (6). A transmission line (9) and a first capacitor (C1) are formed on a resin substrate (1). A first bonding wire (7) connects the first drain pad (5) and one end of the transmission line (9). A second bonding wire (10) connects the second drain pad (6) and one end of the first capacitor (C1). An output terminal (OUT) is connected to the other end of the transmission line (9) and the other end of the first capacitor (C1). A capacitance value of the first capacitor (C1) is selected so as to cause resonance with inductance of the second bonding wire (10).