Op-Amp Current Mirror Capacitor Multiplier for Lower Dominant Pole
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Solution Overview
Problem
Existing amplifier circuit designs face challenges in increasing capacitance on the output terminal to ground without significantly increasing chip area or power consumption.
Innovation Solution
An operational amplifier with a built-in capacitor multiplier that utilizes a current mirror circuit to multiply the equivalent capacitance without adding additional circuits, effectively doubling the capacitance without increasing area or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacitance is increased directly by increasing the size of the capacitor, then the capacitance value is improved, but the chip area occupied by the capacitor increases significantly
Solution Approach 1:
The patent changes the electrical parameters of the existing capacitor by utilizing the current mirror circuit's current amplification effect. The capacitor remains physically the same, but its effective capacitance value is multiplied through the current mirror ratio, achieving capacitance increase without physical size increase
Solution Approach 2:
The current mirror circuit creates a copied and amplified version of the input current, which effectively multiplies the capacitor's influence on the output node. The capacitor's effect is 'copied' and amplified by the current mirror, achieving equivalent capacitance multiplication without adding physical capacitance
2Quantity of substance
If additional capacitance amplification circuits are introduced, then the capacitance value is improved, but the overall circuit area and power consumption increase
Solution Approach 1:
The current mirror circuit serves multiple functions: it provides the primary current amplification function for the operational amplifier while simultaneously acting as a capacitor multiplier. This multi-functionality eliminates the need for separate capacitance amplification circuits, reducing overall circuit complexity
Solution Approach 2:
The patent merges the capacitance multiplication function with the existing current mirror circuit. By coupling the capacitor between the current input terminal and output terminal of the current mirror, the capacitor multiplier function is integrated into the current mirror structure, eliminating additional independent circuits
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for the dominant pole of the amplifier to be pushed towards a lower frequency, saving capacitor area and maintaining circuit efficiency.
Implementation Method 1
The at least one current mirror circuit is configured to generate a current mirror output current on a current output terminal of the at least one current mirror circuit according to a current mirror input current received by a current input terminal of the at least one current mirror circuit
Data Source
AI summary
An operational amplifier with a built-in capacitor multiplier is provided, where the operational amplifier includes an input transistor, a current mirror circuit and a capacitor. The input transistor generates an input current according to an input signal, and the current mirror circuit generates a current mirror output current on a current output terminal of the current mirror circuit according to a current mirror input current corresponding to the input current received by a current input terminal of the current mirror circuit, where the current output terminal is coupled to an amplifier output terminal of the operational amplifier. In addition, a first terminal of the capacitor is coupled to the amplifier output terminal, and a second terminal of the capacitor is coupled to the current input terminal, making an equivalent capacitance of the capacitor seen on the amplifier output terminal be multiplied by the current mirror circuit.