Dual-Transistor Output Circuit With Buffered Mode Switching
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Solution Overview
Problem
Existing power amplification circuits in mobile communication devices experience deterioration in characteristics due to voltage drops caused by the on-resistance of switches when switching bias currents, leading to inefficiencies and increased circuit area requirements.
Innovation Solution
An output circuit comprising a first and second transistor, an operational amplifier, and a switch circuit that controls the output of voltage or current by using control signals to selectively enable either transistor, thereby avoiding voltage drops and reducing circuit area by minimizing the number of switches required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a switch is used to switch bias voltage to cause an amplifier corresponding to an operation mode to operate, then the power amplification circuit can be switched between different operation modes, but a voltage drop caused by the on-resistance of the switch occurs which deteriorates the characteristics of the bias circuit
Solution Approach 1:
The patent introduces a buffer circuit as an intermediary between the switch and the bias circuit. This buffer circuit comprises a transistor whose gate receives the switched bias voltage, and whose source/drain outputs the buffered bias voltage to the bias circuit. The buffer circuit acts as a mediator that isolates the bias circuit from the voltage drops caused by switch on-resistance, thereby preventing deterioration of bias circuit characteristics while maintaining operation mode switching capability.
2Adaptability or versatility
If multiple switches are used to control output paths for different amplifiers, then different operation modes can be controlled, but the circuit area increases
Solution Approach 1:
The patent merges the switching function and buffering function into a single integrated switch circuit structure. The switch circuit comprises transistors that simultaneously perform switching between different operation modes and buffering of the bias voltage/current. By combining these functions, the patent reduces the number of separate components needed, thereby reducing circuit area while maintaining full operation mode control capability.
Solution Approach 2:
The transistors in the switch circuit are designed to perform multiple functions: they act as switches for mode selection and simultaneously serve as buffers for voltage/current output. This multi-functional design eliminates the need for separate buffer circuits for each switch, reducing overall circuit area while maintaining adaptability for different operation modes.
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 prevents or reduces deterioration in characteristics caused by switching, allowing for efficient switching between output voltages or currents without voltage drops, and enables a more compact circuit design by using smaller transistors for switches.
Implementation Method 1
The operational amplifier has a first input terminal and a second input terminal and is configured to output a control voltage corresponding to a difference between a reference voltage supplied to the first input terminal and an input voltage supplied to the second input terminal
Implementation Method 2
The first transistor is configured to output a first output voltage or output current from a drain of the first transistor. The second transistor is configured to output a second output voltage or output current from a drain of the second transistor
Data Source
AI summary
An output circuit includes a first transistor, a second transistor, an operational amplifier that outputs a control voltage, and a switch circuit that controls voltage output in accordance with a control signal. When the control signal is in a first state, the switch circuit supplies the control voltage to the gate of the first transistor to turn on the first transistor and electrically connects the drain of first transistor to the operational amplifier so that a first output voltage is output from the drain of the first transistor. When the control signal is in a second state, the switch circuit supplies the control voltage to the gate of the second transistor to turn on the second transistor and electrically connects the drain of the second transistor to the operational amplifier so that a second output voltage is output from the drain of the second transistor.