Current-Mirror Differential Amplifier Kick Transistors
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Solution Overview
Problem
Conventional semiconductor integrated circuits with current-mirror differential amplifiers face issues with transition time differences between the rise and fall times of input signals, leading to reduced setup/hold margins due to asymmetry and increased power consumption.
Innovation Solution
The integration of additional NMOS transistors as 'kick transistors' between nodes in the current-mirror differential amplifier circuit, along with modifications to the current mirror and differential pair circuits, such as dividing PMOS and NMOS transistors into multiple segments, to control current flow and accelerate signal transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current-mirror differential amplifier is used to receive external minute amplitude signals, then the sensitivity to minute signals is improved, but the transition time difference between rise and fall times increases
Solution Approach 1:
The patent introduces asymmetry into the symmetric current-mirror differential amplifier circuit by adding kick transistors (NMOS transistors) only to one side of the differential pair. This asymmetric modification allows the circuit to accelerate one transition (rise or fall time) without affecting the other, thereby reducing the transition time difference while maintaining the ability to detect minute signals.
Solution Approach 2:
The kick transistors are configured to activate in advance during signal transitions to preemptively accelerate the charging or discharging of the output node. By preparing the current path beforehand through the kick transistors, the circuit reduces the transition time difference before the actual signal level change occurs.
2Loss of time
If the transition time difference is reduced by adding kick transistors, then the setup/hold margins are improved, but the circuit complexity increases
Solution Approach 1:
The patent segments the differential amplifier circuit into distinct functional portions by adding kick transistors as separate components. This segmentation allows independent control and optimization of different transition phases (rise and fall times) without requiring complete redesign of the entire amplifier circuit, thus managing complexity through modular addition.
Solution Approach 2:
The kick transistors act as intermediary elements between the differential pair and the output node. These intermediate components provide a controlled current path that accelerates transitions without directly modifying the core differential amplifier structure, thereby reducing transition time difference while minimizing impact on overall circuit complexity.
3Reliability
If differential signals are compared with each other to improve circuit characteristics, then the performance is improved, but the number of interconnects increases
Solution Approach 1:
The current-mirror differential amplifier circuit serves multiple functions: it compares differential signals to improve reliability while simultaneously providing amplified output signals for further processing. The kick transistors add the capability of transition acceleration without requiring separate dedicated circuits, thus achieving multi-functionality that balances reliability improvement with controlled complexity.
Data Source
AI summary
According to one embodiment, a semiconductor integrated circuit includes first to six transistors and a constant current source circuit. The first and second transistors form a current mirror circuit connected to a first power source node. The third and fourth transistors form a differential pair circuit. The third and fourth transistors receive first and second external signals at their gates, respectively. The constant current source circuit has one end connected to source terminals of the third and fourth transistors, and the other end connected to a second power source node. The fifth and sixth transistors form a current pathway between a common gate node of the first and second transistors and the constant current source circuit. The gate of fifth transistor is connected to a signal output node. The gate of sixth transistor receives a signal of logic opposite to a signal to be obtained at the signal output node.