Differential Pair Bias Switching to Suppress MOSFET BTI Drift
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Solution Overview
Problem
Metal-oxide-semiconductor field-effect transistors (MOSFETs) in differential pair circuits experience characteristic deterioration due to negative bias temperature instability (NBTI) and positive bias temperature instability (PBTI), affecting the reception operation of communication signals, particularly in high-temperature environments.
Innovation Solution
A switchover circuit is introduced to alternate between normal and opposite-phase application states, applying voltages that cancel the DC potential difference between the gate and back gate of MOSFETs, thereby inhibiting characteristic deterioration by fluctuating the gate threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a differential pair circuit uses MOSFETs for signal processing, then the circuit can efficiently process communication signals, but the MOSFETs experience characteristic deterioration due to NBTI and PBTI effects
Solution Approach 1:
The patent applies periodic action by switching the bias voltages of the MOSFET gates between normal and opposite-phase states at regular intervals. This periodic voltage reversal prevents the accumulation of bias stress that causes NBTI and PBTI deterioration, while maintaining continuous signal processing capability through the differential pair configuration
Solution Approach 2:
The patent employs inversion by applying opposite-phase voltages to the MOSFET gates during alternating time periods. This voltage inversion reverses the direction of the electric field between gate and back gate, counteracting the one-directional bias stress that leads to threshold voltage drift and characteristic deterioration
2Stability of the object's composition
If DC potential difference is maintained between gate and back gate of MOSFETs, then the MOSFETs can maintain stable operation, but characteristic deterioration occurs due to NBTI and PBTI
Solution Approach 1:
The bias voltage switching circuit periodically alternates the DC potential difference between gate and back gate, reversing its polarity at set intervals. This periodic reversal maintains operational stability by ensuring the MOSFET remains biased while preventing cumulative degradation from sustained one-directional stress
Solution Approach 2:
The patent changes the voltage parameter by dynamically adjusting the gate bias voltage between two opposite-phase states. This parameter switching maintains the MOSFET in an active operating region while varying the electric field direction to prevent threshold voltage drift caused by fixed bias conditions
3Reliability
If opposite-phase voltages are applied to MOSFET gates, then characteristic deterioration is inhibited, but circuit complexity increases due to switchover requirements
Solution Approach 1:
The bias voltage switching circuit performs multiple functions: it generates opposite-phase voltages, switches between normal and reversed bias states, and synchronizes with the signal processing operation. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby limiting complexity increase
Solution Approach 2:
The patent merges the bias voltage generation and switching functions into a single integrated circuit that works in conjunction with the differential pair. By combining these functions rather than using separate independent circuits, the overall device complexity is minimized while achieving the desired voltage reversal effect
Data Source
AI summary
A deterioration inhibiting circuit includes a switchover circuit that inhibits characteristic deterioration of first and second transistors included in a differential pair circuit having first and second input terminals. A gate of the first transistor is connected to the first input terminal, and a gate of the second transistor is connected to the second input terminal. The switchover circuit executes switchover between a first state and a second state. In the first state, a first voltage is applied to the gate of the first transistor and a second voltage is applied to the gate of the second transistor. In the second state, the second voltage is applied to the gate of the first transistor and the first voltage is applied to the gate of the second transistor. The first voltage is higher than an intermediate voltage, and the second voltage is lower than the intermediate voltage.