Push-Pull Output Driver With Level Shifter for PVT-Stable Bias
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Solution Overview
Problem
Conventional push-pull voltage drivers in operational amplifiers are susceptible to variations in performance due to Process, Supply Voltage, and Temperature (PVT) conditions, leading to inconsistent steady-state current consumption.
Innovation Solution
A voltage driver circuit with a level shifter and a push-pull output stage using transistors in a current mirror configuration, where the first transistor is configured as a source follower and the second as a common source amplifier, with a bias current generator to maintain well-controlled steady-state DC output, implemented using field effect transistors (NMOS, PMOS) or bipolar transistors (NPN, PNP).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional push-pull output drivers are used, then quick adjustment of output voltages is achieved, but performance varies due to PVT conditions
Solution Approach 1:
The patent changes the configuration parameters of the output driver by using a current mirror configuration where the second transistor mirrors the current of the first transistor. This parameter change ensures that the output current is determined by the reference current rather than being directly affected by PVT variations, thereby maintaining performance consistency while preserving the quick voltage adjustment capability
Solution Approach 2:
The current mirror configuration inherently provides a feedback mechanism where the second transistor's current is automatically adjusted to match the first transistor's current based on the reference current. This feedback ensures that variations in PVT conditions are compensated, maintaining reliable performance while enabling fast response
2Speed
If conventional output drivers are used, then push-pull arrangement provides quick voltage adjustment, but steady state current consumption varies
Solution Approach 1:
The patent changes the operating parameters by establishing a controlled current relationship through the current mirror configuration. The steady state current is now determined by the reference current and transistor matching rather than by PVT-dependent parameters, reducing steady state current consumption while maintaining fast response capability
Solution Approach 2:
The current mirror configuration creates a copy of the reference current through the second transistor that mirrors the first transistor's current. This copying mechanism ensures that the output current follows a controlled reference rather than varying with PVT conditions, reducing unnecessary current consumption while preserving quick voltage adjustment
Data Source
AI summary
A voltage driver circuit for an output stage of an operational amplifier, or other circuits, includes a level shifter and an output driver including a source follower and a common source amplifier in a push-pull configuration. The level shifter generates a node voltage as a function of an input voltage on the input node. The output driver including a first transistor having a control terminal receiving the node voltage, and connected between a supply voltage and an output node, and a second transistor having a control terminal receiving the input voltage from the input node, and connected between the output node and a reference voltage, wherein the first and second transistors have a common conductivity type.