Voltage Buffering Circuit With Inductor for Reduced Output Clipping
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Solution Overview
Problem
Voltage followers, such as emitter follower amplifiers, experience non-linearity and output clipping when input voltages exceed manufacturing specifications, leading to distortion and reduced reliability due to diminished drain-to-source voltage of current source MOSFETs, which affects the faithful reproduction of input signals.
Innovation Solution
Incorporating an inductor coupled to the output of the current source MOSFET in the voltage follower circuit to minimize non-linearity and reduce voltage compression, thereby extending the 1 dB compression point and improving linearity, and using bias resistors to maintain MOSFET headroom and prevent clipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage follower amplifier is used to buffer between amplifier stages, then impedance matching and signal isolation are improved, but non-linearity and output clipping occur when input voltages exceed manufacturing specifications
Solution Approach 1:
An inductor is introduced as an intermediary component coupled to the output of the current source MOSFET. This inductor acts as a mediator that prevents direct voltage compression at the MOSFET output, allowing the voltage follower to operate linearly over a wider input voltage range without clipping, thus resolving the harmful non-linearity effect while maintaining reliable signal reproduction
Solution Approach 2:
The patent changes the operating parameters of the voltage follower by adding the inductor, which modifies the voltage-compression characteristics of the current source MOSFET. This parameter change extends the 1 dB compression point and improves linearity, allowing the amplifier to maintain reliable signal reproduction even when input voltages approach or exceed original manufacturing specifications
2Adaptability or versatility
If the input voltage exceeds manufacturing specifications, then the operational range is extended, but drain-to-source voltage diminishes causing clipping and distortion
Solution Approach 1:
The inductor serves as an intermediary that decouples the direct relationship between input voltage and MOSFET drain-to-source voltage. By introducing this intermediate energy storage element, the circuit can accommodate higher input voltages without proportionally reducing the MOSFET's drain-to-source voltage, thus extending operational range while preventing clipping and maintaining signal fidelity
Solution Approach 2:
The inductor provides beforehand cushioning by storing energy during voltage swings and releasing it when needed, preventing sudden voltage drops that would cause clipping. This protective mechanism allows the voltage follower to handle input voltages beyond original specifications without compromising signal reproduction reliability
Data Source
AI summary
In an example apparatus, a first transistor has a base terminal, a first current terminal and a second current terminal. The base terminal is coupled to an input voltage node. A second transistor has a control terminal, a third current terminal and a fourth current terminal. The third current terminal is coupled to the second current terminal. The fourth current terminal is coupled to a first resistor. A second resistor is coupled to the control terminal. An inductor is coupled between the first resistor and a ground terminal.