CMOS Inverter Back-Gate Control for Transconductance Extension
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Solution Overview
Problem
The transconductance range of CMOS inverters is limited by the supply voltage, which restricts the performance of inverter-based circuits like RF receivers.
Innovation Solution
A system and method that includes a biasing circuit and a control circuit to provide a supply voltage and bias voltage to the back gates of transistors, extending the transconductance range beyond the typical supply voltage limits by using a transistor arrangement and a tunable resistor to compensate for voltage and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the supply voltage of the CMOS inverter is increased to extend the transconductance range, then the transconductance range is improved, but the power consumption and device stress increase
Solution Approach 1:
The patent applies parameter changes by utilizing the back gate voltage to modify the threshold voltage of the transistors. By changing the threshold voltage parameter through back gate control, the transconductance range is extended without requiring an increase in supply voltage, thus avoiding increased power consumption while achieving the desired adaptability improvement
Solution Approach 2:
The back gate voltage serves as an intermediary control mechanism. Instead of directly increasing supply voltage to extend transconductance range (which would increase power consumption), the patent uses back gate voltage as an intermediate parameter to indirectly control and extend the transconductance range, thereby resolving the contradiction between adaptability improvement and power consumption increase
2Adaptability or versatility
If the supply voltage is increased to extend the transconductance range, then the transconductance range is improved, but the device reliability and transistor stress worsen
Solution Approach 1:
The patent changes the threshold voltage parameter through back gate control rather than increasing supply voltage. This parameter change approach extends the transconductance range while maintaining the supply voltage at safe levels, thereby improving adaptability without compromising device reliability or increasing transistor stress
Solution Approach 2:
The back gate voltage acts as an intermediary that enables transconductance range extension without directly stressing the transistor channels. By controlling the threshold voltage through the back gate interface, the patent achieves improved adaptability while protecting the main transistor structure from excessive stress, thus maintaining reliability
3Adaptability or versatility
If a bias voltage is applied to the back gates to extend the transconductance range, then the transconductance range is improved, but the control circuit complexity increases
Solution Approach 1:
The patent merges the biasing function with the existing circuit structure by interconnecting the back gates of differential pair transistors to a common bias voltage source. This integration approach extends the transconductance range while minimizing additional circuit complexity, as the biasing functionality is combined with the differential pair structure rather than adding separate complex control circuits
Solution Approach 2:
The back gate bias voltage serves multiple functions simultaneously: it extends the transconductance range, provides threshold voltage control, and enables temperature compensation. This multi-functionality approach achieves improved adaptability without proportionally increasing control circuit complexity, as a single bias voltage source accomplishes multiple control objectives
4Stability of the object's composition
If the transconductance is controlled across temperature variations, then the linearity is improved, but the biasing circuit complexity increases
Solution Approach 1:
The patent uses parameter changes in the back gate voltage to compensate for temperature-induced threshold voltage shifts. By adjusting the back gate bias voltage parameter with temperature, the patent maintains constant transconductance and improved linearity across temperature variations without requiring complex temperature sensing and compensation circuits
Solution Approach 2:
The biasing circuit provides self-service temperature compensation by using the inherent temperature dependence of transistor characteristics. The back gate bias voltage is designed to automatically adjust in response to temperature changes, enabling the circuit to self-regulate and maintain linearity without external temperature control mechanisms, thus improving stability without proportionally increasing complexity
Data Source
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Figure 3A~3B
AI summary
A system (100) is provided for increasing the transconductance of a CMOS inverter (101). The system comprises a biasing circuit (102) configured to provide a supply voltage (Vd) to the CMOS inverter (101), wherein the biasing circuit (102) comprises at least one transistor arrangement, wherein the transistor arrangement and the CMOS inverter (101) are interconnected via back gates of respective transistors. The system further comprises a control circuit (103) configured to provide a bias voltage (Vbg) to the interconnected back gates when the supply voltage (Vd) reaches to a threshold value (Vt), whereby both the biasing circuit (102) and the control circuit (103) together control the transconductance of the CMOS inverter (101) .