Emulated IC Capacitor Circuit for Large Capacitance in Small Area
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Solution Overview
Problem
Integrated circuit capacitors have limited capacitance and are prone to leakage currents, which restrict their use in applications requiring long time constants and adaptability, especially due to temperature dependence and point defects.
Innovation Solution
An electrical circuit that emulates capacitance by using a physical capacitor charged through an amplifier and a reset system, allowing for voltage amplification and charge recycling, effectively multiplying the capacitance value and extending the voltage window without drawing charge from the input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a physical capacitor is used in integrated circuit technology, then capacitance function is achieved, but the capacitance value is limited to approx 10-100 pF due to limited capacitance per area
Solution Approach 1:
An operational amplifier is introduced as an intermediary component between the input signal and the physical capacitor. The amplifier multiplies the input voltage by a factor M (where M > 1), causing the capacitor to experience a larger voltage swing than the actual input signal. This voltage multiplication effect emulates a larger capacitance value at the input terminal, resolving the contradiction between achieving high capacitance and minimizing area.
Solution Approach 2:
The circuit changes the voltage parameter through amplification. By applying a gain factor M to the input voltage, the physical capacitor operates at a scaled-up voltage level, which creates the electrical behavior of a larger capacitor at the input. This parameter transformation allows the system to achieve emulated capacitance values much larger than the physical capacitor's actual value, effectively resolving the area-capacitance tradeoff.
2Reliability
If a physical capacitor is used, then capacitance function is achieved, but leakage current increases significantly when circuitry is connected, especially at high temperatures above 150°C
Solution Approach 1:
The operational amplifier acts as a buffer between the input circuitry and the physical capacitor. This intermediary isolation prevents direct interaction between external circuit elements and the capacitor, reducing the impact of temperature-dependent leakage currents. The amplifier's high input impedance and controlled output impedance create a more stable electrical environment, mitigating leakage effects even at elevated temperatures.
3Adaptability or versatility
If a physical capacitor is used, then capacitance function is achieved, but the capacitance value cannot be adapted during operation
Solution Approach 1:
The circuit introduces dynamic adaptability through the amplifier's gain factor M, which can be adjusted during operation. By dynamically changing the amplification factor, the emulated capacitance value (Cemulated = M × Cphysical) can be adapted in real-time without physically changing the capacitor. This dynamic parameter adjustment enables the system to optimize capacitance values based on operating conditions, temperature, and circuit requirements, providing versatility that static physical capacitors cannot achieve.
4Area of stationary object
If a small physical capacitor is used to save area, then area is reduced, but the voltage window is limited
Solution Approach 1:
The operational amplifier performs parameter transformation by multiplying the input voltage by factor M before applying it to the physical capacitor. This allows the small physical capacitor to experience a large voltage swing (M times the input voltage range) while the actual input voltage remains within a safe, limited range. The amplifier effectively expands the voltage window available to the input circuitry without requiring the physical capacitor to withstand proportionally higher voltages, thus saving area while maintaining operational flexibility.
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
This solution enables the creation of a large emulated capacitance using a small physical capacitor, reducing leakage current effects and allowing for adaptable capacitor values, thus saving area and cost while enabling new circuit solutions.
Implementation Method 1
an amplifier for amplifying the voltage at the input of the electrical circuit such that the physical capacitor is charged with a larger change in voltage than the change in voltage at the input
Implementation Method 2
a physical capacitor which is charged by charge flow from the input of the electrical circuit
Implementation Method 3
a reset system for resetting the state of charge of the physical capacitor without drawing charge from the input of the electrical circuit
Data Source
AI summary
An electrical circuit for emulating a capacitance, comprises a physical capacitor which is charged by charge flow from the input of the electrical circuit. An amplifier amplifies the voltage at the input of the electrical circuit such that the physical capacitor is charged with a larger change in voltage than the change in voltage at the input. This implements an effective multiplication of capacitance. A reset system resets the physical capacitor without drawing charge from the input of the electrical circuit. This extends the voltages which can be provided to the input.