Neutralized Amplifier Circuit Layout for 500 GHz Stability
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Solution Overview
Problem
Existing neutralization circuits in ultra-high frequency bands, such as 500 GHz, face challenges in achieving the required small inductance values due to physical constraints, making it impossible to implement amplifier circuits effectively.
Innovation Solution
Incorporating a series connection of transmission lines and capacitors or coupling lines in the neutralization circuit to achieve the necessary inductance values, allowing for a layout that can neutralize feedback capacitance in ultra-high frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transmission line neutralization circuit is used to neutralize feedback capacitance at 500 GHz, then the inductance value must be very small (10 pH or less), but the transmission line length becomes extremely short (20 μm or less), making it impossible to arrange the circuit in actual layout
Solution Approach 1:
The neutralization circuit is segmented into multiple transmission line sections with different electrical characteristics. By dividing the single transmission line into multiple segments connected in series, the circuit achieves the required small equivalent inductance while each segment can be laid out with reasonable length, solving the layout feasibility problem.
Solution Approach 2:
The invention changes the electrical parameters of the transmission line segments, specifically using lines with different characteristic impedances (e.g., 50Ω and 25Ω lines). By adjusting these parameters and their lengths, the equivalent inductance is controlled to achieve neutralization at 500 GHz while maintaining practical layout dimensions.
2Ease of operation
If the transmission line length is increased to achieve practical layout, then the inductance value increases beyond the required 10 pH, making neutralization at 500 GHz impossible
Solution Approach 1:
By changing the characteristic impedance parameter of transmission line segments and adjusting their lengths, the invention achieves the required small equivalent inductance value. The combination of different impedance lines with specific lengths allows precise control of the total inductance while using practical transmission line dimensions for layout.
3Device complexity
If a single transmission line is used for neutralization, then the circuit is simple, but the inductance value cannot be sufficiently reduced for ultra-high frequency operation
Solution Approach 1:
The neutralization circuit is divided into multiple transmission line segments connected in series. This segmentation increases the degree of freedom in designing the equivalent inductance, allowing the total inductance to be reduced to the required level for 500 GHz operation while maintaining a relatively simple overall circuit structure.
Solution Approach 2:
Multiple transmission line segments with different electrical characteristics are merged in series to achieve the desired equivalent inductance. By combining these segments, the circuit achieves better inductance control compared to a single transmission line, enabling effective neutralization at ultra-high frequencies.
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 enables the implementation of amplifier circuits with neutralization circuits in ultra-high frequency bands, achieving a large gain and stability at frequencies up to 500 GHz while preventing out-of-band gain and oscillation.
Implementation Method 1
A neutralization circuit is a circuit having a function of canceling (neutralizing) a feedback capacitance between an input and an output, which is a factor that reduces a gain of a transistor, through resonance with an inductance provided outside the transistor.
Data Source
AI summary
An amplifier circuit includes source-grounded amplifiers and a neutralization circuit that is connected between drain terminals and gate terminals of the source-grounded amplifiers and neutralizes a feedback capacitance of the source-grounded amplifiers, and the neutralization circuit includes transmission lines and a capacitor connected in series.