Differential Amplifier Layout for High Output Power at High Cutoff Frequency
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Solution Overview
Problem
Existing high-frequency differential amplifiers face a trade-off between output power and cutoff frequency due to increased input capacitance when transistor size is increased, leading to suboptimal performance in both aspects.
Innovation Solution
The amplifier circuit employs a configuration with parallel transistors and RC circuits to maintain input capacitance while doubling output power, using a distributed amplifier with a gain and power amplifier stage, and incorporating bias signals to shield high-frequency signals, thereby improving the trade-off between output power and cutoff frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transistor size is increased to increase output power, then the output power is improved, but the input capacitance increases and the cutoff frequency decreases
Solution Approach 1:
The amplifier is divided into multiple unit amplifiers connected in parallel, each with its own transistor. This segmentation allows the total output power to be increased by adding more units without requiring a single large transistor, thereby avoiding the input capacitance increase that would lower the cutoff frequency.
Solution Approach 2:
Multiple unit amplifiers are combined in parallel configuration, merging their output powers while maintaining individual transistor sizes. This combining approach achieves high output power without the penalty of increased input capacitance that would occur with a single large transistor.
2Power
If parallel transistors are used to double output power, then the output power is improved, but the input capacitance increases
Solution Approach 1:
The amplifier configuration segments the total power output requirement into multiple smaller transistor units. Each transistor maintains its original size and capacitance characteristics, so the total input capacitance remains comparable to a single transistor design while achieving doubled output power through parallel operation.
Data Source
AI summary
Provided is an amplifier circuit including: a unit amplifier, wherein the unit amplifier includes a first transistor in which a first input signal is input to a first control terminal and which generates a first output signal, a second transistor in which a second input signal is input to a second control terminal and which generates a second output signal differential from the first output signal, a third transistor which is provided in parallel with the first transistor and generates a third output signal differential from the first output signal, and a fourth transistor which is provided in parallel with the second transistor and generates a fourth output signal differential from the second output signal, the first and fourth output signals are merged to be output to a first output transmission path, and the second and third output signals are merged to be output to a second output transmission path.