Cascode Inverting Amplifier Clamp Circuit for Faster Settling
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Solution Overview
Problem
Inverting amplifiers with cascode transistors suffer from reduced drive power, leading to degraded large-signal characteristics and increased settling time in integrators, particularly in high-speed applications such as image sensors and AD converters.
Innovation Solution
The introduction of a clamp circuit with switches and capacitors connected to the gates of transistors in an inverting amplifier configuration, allowing for dynamic adjustment of gate voltages and enhancing drive power by controlling current flow through cascode transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cascode transistors are used in inverting amplifier configuration, then gain is improved, but drive power is reduced and settling time is increased
Solution Approach 1:
The clamp circuit dynamically adjusts the gate voltages of the cascode transistors based on the input signal amplitude. During large-signal transitions, the clamp circuit activates to provide additional drive current by temporarily modifying the gate voltage of the cascode transistors, thereby enhancing their current driving capability without compromising the high-gain configuration.
Solution Approach 2:
The clamp circuit acts as an intermediary between the input signal and the cascode transistors. It introduces auxiliary voltage control signals that mediate the interaction between the input signal and the transistor gates, providing enhanced drive power during critical transition periods while maintaining the overall high-gain architecture.
2Measurement precision
If cascode transistors are used in inverting amplifier configuration, then gain is improved, but settling time is increased
Solution Approach 1:
The clamp circuit performs preliminary action by pre-charging or pre-discharging the gate capacitances of the cascode transistors before the main signal transition occurs. This preliminary voltage adjustment reduces the time required for the transistors to respond to large-signal inputs, thereby accelerating the settling process while maintaining the high-gain configuration.
Solution Approach 2:
The clamp circuit dynamically modifies the operating point of the cascode transistors during signal transitions, enabling faster switching and reduced settling time. By temporarily altering the gate voltages, the circuit optimizes the transistor response speed without permanently compromising the high-gain configuration.
3Power
If clamp circuit is added to inverting amplifier, then drive power is enhanced and settling time is reduced, but device complexity is increased
Solution Approach 1:
The clamp circuit is merged with the existing inverting amplifier structure by sharing common nodes and utilizing the same power supply rails. The clamp circuit's switches and capacitors are integrated into the existing transistor gate connections, reducing the need for separate dedicated components and minimizing overall circuit complexity.
Solution Approach 2:
The clamp circuit components (switches and capacitors) serve multiple functions: they provide drive power enhancement, accelerate settling, and maintain high-gain operation. By making these components multi-functional, the patent reduces the need for additional dedicated components, thereby limiting the increase in device complexity.
Data Source
AI summary
An inverting amplifier includes an input terminal, an output terminal, a PMOS transistor, another PMOS transistor, an NMOS transistor, another NMOS transistor, and a clamp circuit. The PMOS transistors are connected in series between a supply voltage and an output terminal. The NMOS transistors are connected in series between a ground voltage and the output terminal. The clamp circuit is connected to the gate of the other PMOS transistor and the gate of the other NMOS transistor. The clamp circuit includes a switch, a capacitor, another switch, and another capacitor. At least one of the gate of the PMOS transistor and the gate of the NMOS transistor is connected to the input terminal.