Common-Source Differential Power Amplifier With Capacitance Compensation
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Solution Overview
Problem
Differential power amplifiers experience phase distortion as input signal power increases due to varying gate-source and gate-drain parasitic capacitances, leading to inconsistent phase offsets in output signals.
Innovation Solution
A common-source differential power amplifier is designed with a compensation circuit and paired driving transistors, where both transistors are either NMOS or PMOS, with equal source potentials and drains connected to differential signal output terminals. The compensation circuit includes two transistors with short-circuited sources and drains connected to each other's gates, and signal terminals connected to differential input terminals directly or through capacitors, allowing capacitance adjustment to maintain constant input capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the input signal power of the differential power amplifier increases, then the output signal power increases, but the phase offset of the output signal increases resulting in phase distortion
Solution Approach 1:
The patent changes the electrical parameters of the compensation transistors (specifically their capacitance characteristics) to counteract the varying parasitic capacitances of the driving transistors. By carefully selecting the capacitance values of the compensation transistors, the total input capacitance remains constant despite changes in input signal power, thereby maintaining constant phase offset and suppressing phase distortion.
2Power
If the gate-source parasitic capacitance and gate-drain parasitic capacitance of the driving transistor increase with input signal power, then the output signal power increases, but the input capacitance varies causing phase distortion
Solution Approach 1:
The patent converts the harmful effect of varying parasitic capacitances into a beneficial constant total capacitance. The compensation transistors are designed with specific capacitance characteristics that complement the varying parasitic capacitances of the driving transistors, such that their sum remains constant across different input signal power levels. This transforms the problem of varying capacitance into a solution where the total capacitance is stabilized.
3Reliability
If a compensation circuit is added to maintain constant input capacitance, then phase distortion is suppressed, but the device complexity increases
Solution Approach 1:
The patent introduces asymmetric compensation elements (compensation transistors with specific capacitance values) into the symmetric differential amplifier structure. The compensation transistors are configured with different capacitance values to precisely counterbalance the asymmetric variations in parasitic capacitances of the driving transistors, achieving constant total input capacitance while maintaining the overall differential symmetry for signal processing.
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
This configuration suppresses phase distortion by maintaining constant input capacitance as input signal power increases, reducing signal delay and phase distortion in the output signal.
Implementation Method 1
each of the first compensation transistor and the second compensation transistor constitutes a capacitor. As the input signal power of the common-source differential power amplifier increases, the capacitance value of the first compensation transistor and the second compensation transistor connected in parallel decreases. By adjusting the parameters (e.g., doping concentration, size, etc.) of each compensation transistor, the input capacitance of the two differential signal input terminals of the differential power amplifier can be kept at a constant value
Implementation Method 2
a source and a drain of the first compensation transistor are short-circuited and connected to a gate of the second compensation transistor and one of the two signal terminals of the compensation circuit, and a source and a drain of the second compensation transistor are short-circuited and connected to a gate of the first compensation transistor
Data Source
AI summary
A common-source differential power amplifier comprises a compensation circuit, which comprises a first and a second compensation transistors and two signal terminals, a source and a drain of the first compensation transistor are short-circuited and connected to a gate of the second compensation transistor and one signal terminal of the compensation circuit, the source and the drain of the second compensation transistor are short-circuited and connected to the gate of the first compensation transistor and the other signal terminal of the compensation circuit, the two signal terminals of the compensation circuit are further respectively connected to two differential signal input terminals of the common-source differential power amplifier directly or via a capacitor, where the first and second compensation transistors in the same compensation circuit are both NMOS transistors or both PMOS transistors. An electronic device including the power amplifier is also disclosed.