Compensation Circuit Amplifying Small Capacitor
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Solution Overview
Problem
Miller compensation circuits require large capacitance and resistance values to achieve desired frequency zeros, leading to increased chip area and unsatisfactory compensation effects when smaller capacitors are used.
Innovation Solution
The compensation circuit amplifies a small capacitor by incorporating a second transconductance amplifier and resistor, effectively increasing the equivalent capacitance, thereby achieving a good compensation effect with minimal chip area and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large capacitance and resistance values are used in Miller compensation circuit, then the desired frequency zero is achieved, but the chip area is greatly increased
Solution Approach 1:
The patent changes the effective capacitance parameter by introducing a transconductance amplifier in a positive feedback configuration. The capacitor C is bootstrapped such that its effective capacitance becomes Ceff = C*(1 + gm2*R2), where gm2 is the transconductance of the second amplifier and R2 is the feedback resistance. This parameter transformation allows a small physical capacitor to provide the effect of a large capacitor, resolving the contradiction between compensation effectiveness and chip area.
Solution Approach 2:
The patent introduces a second transconductance amplifier (gm2) and resistance R2 as intermediary elements. These intermediaries create a positive feedback loop that bootstraps the capacitor C, transforming its effective capacitance value without requiring physical enlargement of the capacitor itself. The intermediary amplifier circuit enables the small capacitor to achieve the compensation effect of a large capacitor.
2Area of stationary object
If capacitor with smaller capacitance is used, then the chip area is reduced, but the compensation effect is not satisfactory
Solution Approach 1:
The patent applies parameter transformation by bootstrapping the capacitor C through positive feedback. The effective capacitance parameter Ceff is changed to C*(1 + gm2*R2), allowing a small physical capacitor to provide large capacitance effect. This resolves the contradiction by maintaining compensation effectiveness while using smaller physical components.
Solution Approach 2:
The second transconductance amplifier gm2 and resistance R2 serve as intermediaries that transform the capacitance parameter. They create a feedback mechanism that multiplies the effective capacitance of the small capacitor C, enabling satisfactory compensation effect with minimal chip area.
Data Source
AI summary
An improved compensation circuit with loop compensation is disclosed. The compensation circuit can get an equivalent large capacitance by amplifying a small capacitor. Hence, the compensation circuit can get a good compensation effect with a minimum chip area, hence lower cost.