Push-Pull Source Follower Biasing for Independent Current and Voltage Control
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Solution Overview
Problem
The push-pull source follower design faces challenges in independently programming bias current and output mean voltage, which affects its performance and efficiency.
Innovation Solution
A push-pull source follower circuit is designed with independent biasing circuits to program bias current and output mean voltage, utilizing transistors and biasing circuits with error amplifiers and low-pass filters to adaptively adjust bias voltages based on input voltages and reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a push-pull source follower uses a complementary structure with PMOS and NMOS transistors, then gain and power efficiency are improved, but independent programming of bias current and output mean voltage becomes difficult
Solution Approach 1:
The biasing system is segmented into two independent biasing circuits: a first biasing circuit that independently programs the bias current by controlling the tail current, and a second biasing circuit that independently programs the output mean voltage by controlling the gate voltages of the push-pull transistors. This segmentation allows each parameter to be controlled separately without interfering with the other, resolving the contradiction between achieving high power efficiency through complementary structure and managing the complexity of independent parameter programming.
Solution Approach 2:
The patent introduces intermediary biasing circuits that act as mediators between the control inputs and the push-pull transistors. These intermediary circuits (including voltage generators, error amplifiers, and low-pass filters) translate control signals into appropriate bias voltages and currents, enabling independent programming of bias current and output mean voltage while maintaining the benefits of the complementary push-pull structure.
2Device complexity
If a single source follower is used, then the structure is simple, but gain and output impedance performance are insufficient
Solution Approach 1:
The patent merges a PMOS source follower and an NMOS source follower into a complementary push-pull configuration. This merging allows the circuit to leverage the advantages of both transistor types, achieving higher gain and better power efficiency compared to a single source follower, while the independent biasing circuits manage the increased complexity to maintain controllable performance.
3Loss of energy
If push-pull biasing is implemented, then power efficiency improves, but independent control of bias parameters becomes an obstacle
Solution Approach 1:
The patent implements dynamic biasing control where the biasing circuits can independently and adaptively adjust the bias current and output mean voltage based on operational requirements. The first biasing circuit dynamically controls the tail current to program bias current, while the second biasing circuit dynamically adjusts gate voltages to program output mean voltage, providing flexible and independent parameter control that enhances ease of operation while maintaining high power efficiency.
Data Source
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AI summary
A push-pull source follower circuit (100) includes a main source follower (102), a first biasing circuit (104), and a second biasing circuit (106). The main source follower (102) includes a first transistor and a second transistor between a first power rail and a second power rail, where the first transistor and the second transistor include an N-type transistor and a P-type transistor. The first biasing circuit (104) programs a bias current of the main source follower (102) through generating a first bias voltage of the first transistor. The second biasing circuit (106) programs an output mean voltage of the push-pull source follower circuit (100) through generating a second bias voltage of the second transistor. The bias current and the output mean voltage are programmed independently.