Current-Mode Logic Cascode Circuit for Wider Output Swing
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Solution Overview
Problem
Current mode logic circuits face challenges in maintaining high output voltage levels without transistor breakdown due to reduced voltage tolerance with transistor miniaturization, leading to decreased output voltage and increased noise interference.
Innovation Solution
A current mode logic circuit design incorporating trim resistors and cascode transistors with controlled voltage inputs and AC coupling capacitors to manage voltage magnitudes, allowing stable operation and increased output swing width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the magnitude of the voltage applied to the drain node of the differential transistor is increased to increase the output voltage level, then the output voltage level is improved, but the transistor device breaks down due to exceeding the voltage range
Solution Approach 1:
The circuit is divided into two independent differential amplifier circuits operating in parallel. Each circuit handles one polarity of the output voltage (positive or negative), allowing the voltage stress to be segmented and managed separately. This segmentation enables each transistor to operate within safe voltage limits while the combined output achieves the desired high voltage level.
Solution Approach 2:
A control circuit acts as an intermediary between the input signal and the differential transistor pairs. This control circuit dynamically selects which differential amplifier circuit (positive or negative polarity) should be active based on the input signal polarity, preventing voltage breakdown by ensuring only one circuit operates at a time with controlled voltage application.
2Area of moving object
If transistor sizes are reduced to improve integration density, then device durability deteriorates and the maximum applicable voltage decreases, but high output voltage is required
Solution Approach 1:
By segmenting the output voltage generation into two separate differential amplifier circuits (positive and negative polarity), each using small transistors operated within their reduced voltage tolerance, the circuit achieves high overall output voltage capability without requiring large, durable transistors. Each segmented circuit operates independently within safe voltage limits.
Solution Approach 2:
The invention changes the operating parameters by using dynamic voltage control and polarity switching. Instead of applying high voltage continuously to small transistors, the system alternates between positive and negative polarity modes, with each mode applying controlled voltage within the reduced tolerance limits of the miniaturized transistors.
3Reliability
If the voltage applied to the drain node is limited to maintain device stability, then the output voltage level decreases, but high output voltage is needed for signal quality
Solution Approach 1:
The output voltage is segmented into two polarities, each generated by a separate differential amplifier circuit. By switching between these segmented circuits based on input signal polarity, the system achieves high overall output voltage while each individual circuit operates at stable, limited voltage levels that ensure device reliability.
Solution Approach 2:
The circuit employs dynamic switching between positive and negative polarity differential amplifier circuits based on the input signal. This dynamic operation allows the output voltage to reach high levels by alternating between two stable operating modes, each maintaining device stability through controlled voltage application.
Data Source
AI summary
According to an aspect, a current mode logic circuit comprise a first trim resistor and a second trim resistor connected to a supply voltage, a first transistor connected to an input voltage, a second transistor connected to an inverted input voltage and a third transistor and a fourth transistor connected to the first transistor and the second transistor, respectively, in a cascode manner in order to control magnitudes of an output voltage and an inverted output voltage of the current mode logic circuit.