Self-Biased Telescopic OTA for High Gain and Symmetric Output
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Solution Overview
Problem
Conventional operational transconductance amplifiers (OTAs) face issues with high power consumption, increased circuit area due to additional biasing circuitry, and compromised performance in second-order harmonic rejection and Power Supply Rejection Ratio (PSRR) due to cascode transistor biasing.
Innovation Solution
A telescopic cascode topology-based OTA circuit where cascode transistors are self-biased without additional biasing circuitry, utilizing pairs of transistors to achieve high gain with reduced current consumption and symmetrical output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If additional biasing circuitry is used to bias cascode transistors, then the amplifier can achieve high gain, but power consumption increases and circuit area increases
Solution Approach 1:
The cascode transistors are self-biased using their own gate connections without requiring external biasing circuitry. The gates of the cascode transistors are connected to the drains of the input transistors, allowing the circuit to bias itself and eliminate the need for additional biasing components, thereby reducing power consumption and circuit area while maintaining high gain capability
2Power
If additional biasing circuitry is used to bias cascode transistors, then the amplifier can achieve high gain, but circuit area increases
Solution Approach 1:
The cascode transistors are self-biased using their own gate connections without requiring external biasing circuitry. The gates of the cascode transistors are connected to the drains of the input transistors, allowing the circuit to bias itself and eliminate the need for additional biasing components, thereby reducing power consumption and circuit area while maintaining high gain capability
Solution Approach 2:
The biasing function is merged with the existing transistor connections. The gate connections of the cascode transistors are combined with the drain connections of the input transistors, eliminating separate biasing circuits and reducing the overall circuit area while maintaining the necessary biasing for high gain operation
3Device complexity
If single-ended signals are used, then the circuit is simpler, but performance in second-order harmonic rejection, CMRR, and PSRR degrades
Solution Approach 1:
The patent employs fully differential signals rather than single-ended signals, creating a symmetric differential structure that inherently provides better second-order harmonic rejection, CMRR, and PSRR. The differential configuration allows opposing signals to cancel out even-order harmonics and reject common-mode disturbances, improving reliability without excessive complexity
Data Source
AI summary
A circuit for implementing an operational transconductance amplifier (OTA) based on telescopic topology, wherein cascode transistors of the operational transconductance amplifier (OTA) are self-biased without using additional biasing circuitry, which not only reduces power consumption but also achieves high gain without extra current, and each cascode stage of the OTA has a pair of transistors so that the swing of the output differential signals of the OTA can be completely symmetrical so as to benefit second-order harmonic rejection, CMRR and PSRR.