Cascode Amplifier Gain Control Using Variable Resistance
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Solution Overview
Problem
Existing variable gain amplifiers face limitations in controlling gain outside a linear range, leading to excessive gain reduction and difficulty in fine-tuning attenuation due to voltage constraints on field effect transistors.
Innovation Solution
Incorporating a variable resistance unit between cascode-connected transistors to control gain by varying resistance values, allowing for discrete adjustments without voltage limitations, and using switches and resistors to facilitate gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If voltage control is used to adjust gain in field effect transistors, then gain can be controlled within a linear area, but the control range is limited and gain decreases excessively when voltage falls below a certain value
Solution Approach 1:
The patent changes the control parameter from voltage to resistance. By using a variable resistance unit instead of voltage control, the gain can be adjusted over a wider range without the limitation of the linear area constraint. The resistance value can be varied continuously to achieve fine-grained gain control beyond what voltage control can provide.
Solution Approach 2:
The patent substitutes the electrical voltage control mechanism with a resistance-based control mechanism. This replacement allows for a different physical domain of control that is not constrained by the same limitations as voltage control in field effect transistors, enabling extended gain adjustment range.
2Measurement precision
If voltage control is used for gain adjustment, then gain can be controlled within linear area, but fine adjustment of attenuation becomes difficult when voltage is below certain value
Solution Approach 1:
By changing from voltage control to resistance control, the patent enables continuous and fine-grained adjustment of gain. The variable resistance unit provides a control mechanism that is not constrained by the minimum voltage threshold, allowing for precise attenuation adjustment across the entire gain range.
3Quantity of substance
If cascode amplifier circuit with field effect transistors is used, then power consumption is reduced and size is minimized, but gain control is limited to linear area
Solution Approach 1:
The patent introduces a variable resistance unit as an intermediary element in the cascode amplifier circuit. This intermediary component enables extended gain control capability without requiring changes to the core cascode amplifier structure, thus maintaining the benefits of low power consumption and compact size while adding versatility.
Data Source
AI summary
An amplifier according to an embodiment of the present invention includes a first transistor and a second transistor that are connected between a ground point and a power supply. A control terminal of the first transistor is connected to an input terminal. A first terminal of the first transistor is connected to the ground point. A second terminal of the second transistor is connected to an output terminal. The amplifier further includes an impedance element and a variable resistance unit. The impedance element is connected between the second terminal of the second transistor and the power supply. The variable resistance unit is connected between the second terminal of the first transistor and the first terminal of the second transistor.