Amplifying circuit having supplemental transconductance and stable common-mode feedback
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Solution Overview
Problem
Existing multistage amplifiers do not effectively utilize the potential of the loading circuit to contribute to transconductance, limiting the bandwidth and common-mode stabilization of the amplifying circuit.
Innovation Solution
Incorporating a transconductance and loading circuit that enhances the contribution of the input-stage, loading, and output-stage circuits to the overall transconductance, thereby increasing the bandwidth and improving common-mode stabilization by configuring a second amplifying circuit with a pair of PMOS and NMOS transistors between high and low-voltage terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional multistage amplifier is used with separate input-stage, loading, and output-stage circuits, then the circuit structure is simple and easy to manufacture, but the bandwidth is limited because the loading circuit does not contribute to transconductance
Solution Approach 1:
The patent merges the loading circuit with the transconductance function by coupling the loading circuit between the high-voltage terminal and the input-stage circuit, and configuring it to output a transconductance-enhancement signal to intermediate nodes according to the first amplified signal. This integration allows the loading circuit to simultaneously perform loading and transconductance enhancement functions, thereby increasing bandwidth without proportionally increasing circuit complexity
Solution Approach 2:
The loading circuit is designed to perform multiple functions: it serves as both a loading circuit and a transconductance enhancement circuit. By configuring the loading circuit to receive the first amplified signal and output a transconductance-enhancement signal to the intermediate nodes, it contributes to both the loading function and the transconductance of the second amplifying circuit, achieving multi-functionality that resolves the contradiction between bandwidth and circuit complexity
2Speed
If the loading circuit only functions as a loading, then the circuit design is simple, but the potential to contribute to transconductance is not developed, limiting bandwidth
Solution Approach 1:
The loading circuit is merged with transconductance enhancement functionality by adding feedback paths that allow it to receive the first amplified signal and generate a transconductance-enhancement signal. This combination enables the loading circuit to contribute to both loading and transconductance, increasing bandwidth while maintaining reasonable design simplicity
Solution Approach 2:
The loading circuit is configured with feedback mechanisms where it receives the first amplified signal from the first amplifying circuit and uses this signal to generate a transconductance-enhancement signal that is fed back to the intermediate nodes of the second amplifying circuit. This feedback configuration enables the loading circuit to dynamically adjust and contribute to transconductance, thereby increasing bandwidth without significantly complicating the circuit design
Data Source
AI summary
An amplifying circuit allows its loading circuit to contribute a transconductance to increase the bandwidth of the amplifying circuit, and thereby achieves common-mode stabilization. The amplifying circuit includes a first and a second amplifying circuit. The first amplifying circuit is coupled between a high-voltage terminal and a low-voltage terminal, and outputs a first amplified signal according to an input signal. The second amplifying circuit includes: an input-stage circuit configured to receive the input signal and output an input-stage output signal to intermediate nodes; a transconductance and loading circuit coupled between the high-voltage terminal and the input-stage circuit, and configured to output a transconductance-enhancement signal to the intermediate nodes according to the first amplified signal; and an output-stage circuit coupled between the high-voltage terminal and the low-voltage terminal and coupled to the intermediate nodes, and configured to output an output signal according to the input-stage output signal and the transconductance-enhancement signal.