Differential Amplifier Switch Topology for Leakage Cancellation
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Solution Overview
Problem
Existing amplifiers face challenges in securing dynamic range (DR) due to leakage signals generated by parasitic capacitance in the RF stage, which are not effectively addressed by traditional gain adjustments in the Tx chain, leading to asymmetry and increased area.
Innovation Solution
An amplifier design incorporating a switch that forms a short-circuit path between common source transistors to cancel leakage components by complementary operation, preventing parasitic capacitance effects when turned off, and maintaining DR by adjusting gain through differential input and output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gain of the driver amplifier is increased by adjusting the transistor size, then the dynamic range is improved, but leakage signals are generated
Solution Approach 1:
The switch is configured to turn on when the driver amplifier turns off, proactively creating a discharge path for parasitic capacitance before leakage signals can be generated. This preliminary action prevents the harmful effect rather than correcting it after occurrence.
Solution Approach 2:
The switch acts as an intermediary element that provides a controlled discharge path for the parasitic capacitance of the common gate transistor. By introducing this intermediate component, the patent enables safe dissipation of stored energy without affecting the normal amplification function.
2Reliability
If a separate path for variable gain amplifier is implemented, then the dynamic range is secured, but the area increases and channel asymmetry occurs
Solution Approach 1:
The patent combines the leakage cancellation function with the existing driver amplifier structure by integrating a switch into the common gate configuration. This merging approach eliminates the need for separate cancellation paths while achieving the same dynamic range performance.
Solution Approach 2:
The switch in the common gate configuration serves multiple functions: it enables gain adjustment for the driver amplifier and simultaneously provides a discharge path for parasitic capacitance. This multi-functionality replaces what would otherwise require separate dedicated circuits.
3Reliability
If a separate path for variable gain amplifier is implemented, then the dynamic range is secured, but channel asymmetry of load impedance occurs
Solution Approach 1:
The leakage cancellation function is merged into the symmetric common gate structure of the differential amplifier. By using identical switch configurations in both differential branches, the patent maintains channel symmetry while achieving dynamic range improvement.
Solution Approach 2:
The patent applies the same switch configuration and control mechanism to both differential channels, ensuring homogeneous treatment of signal paths. This homogeneous approach prevents impedance asymmetry while providing effective leakage cancellation in both channels.
Data Source
AI summary
Disclosed is an amplifier that includes a first-first (1-1) transistor and a first-second (1-2) transistor to which differential input signals are applied to gate terminals, respectively; a second-first (2-1) transistor including: one end connected to the 1-1 transistor, a gate terminal configured to receive an operating signal, and the other end configured to output one of differential output signals; a second-second (2-2) transistor including: one end connected to the 1-2 transistor, a gate terminal configured to receive the operating signal, and the other end configured to output the other one of the differential output signals; and a switch connected to one end of the 1-1 transistor and one end of the 1-2 transistor. The switch is configured to turn on based on the 1-1 transistor, the 1-2 transistor, the 2-1 transistor, and the 2-2 transistor being turned off.