Name: capacitance multiplier circuit for larger capacitance
Uploaded: 2025-05-22T09:06:15.000Z
Duration: 1 min 20 s
Channel: JoVE

Los circuitos multiplicadores de capacitancia se utilizan en circuitos integrados para producir un múltiplo de una capacitancia física pequeña cuando se requiere una capacitancia de alto valor.
Estos circuitos están diseñados utilizando una combinación de amplificadores operacionales, resistencias y condensadores.
El primer amplificador operacional del circuito funciona como un seguidor de voltaje, mientras que el segundo amplificador operacional actúa como un amplificador inversor.
El seguidor de voltaje aísla la capacitancia formada por el circuito de la carga impuesta por el amplificador inversor.
Como no entra corriente en los terminales de entrada del amplificador operacional, la corriente de entrada fluye a través del condensador de retroalimentación.
Mediante la aplicación de KCL, se obtiene una relación entre el voltaje de entrada y salida en términos de resistencias, que se puede sustituir en la expresión de corriente.
La reorganización de las expresiones ayuda a determinar la impedancia de entrada.
Al seleccionar los valores de resistencia apropiados, se puede generar una capacitancia efectiva entre el terminal de entrada y la tierra, que es un múltiplo de la capacitancia física.
Para evitar que los amplificadores operacionales se saturen, la capacitancia efectiva está limitada por el voltaje de salida invertido. A medida que aumenta la multiplicación de la capacitancia, el voltaje de entrada máximo permitido debe disminuir.

ejemplo de diseño: multiplicador de capacitancia

En la tecnología de circuitos integrados, a menudo se utiliza un multiplicador de capacitancia para producir un valor de capacitancia mayor cuando una capacitancia física pequeña es insuficiente. Esto se logra mediante un circuito que multiplica los valores de capacitancia por un factor de hasta 1000, de modo que un capacitor de 10 pF puede replicar el rendimiento de un capacitor de 100 nF. El circuito ilustrado en la Figura 1 a continuación incorpora dos amplificadores operacionales: el primero funciona como seguidor de voltaje y el segundo actúa como amplificador inversor. <img alt="Figure1" src="/files/ftp_upload/15176/15176_PT_Figure_1.svg" style="text-align: center; height: 200px;"> Figura 1: Multiplicador de capacitancia El seguidor de voltaje funciona para aislar la capacitancia creada por el circuito de la carga incurrida por el amplificador inversor. Dado que no ingresa corriente a los terminales de entrada del amplificador operacional, el capacitor de retroalimentación transporta la corriente de entrada. Al aplicar la Ley de Corrientes de Kirchhoff (KCL), se puede establecer una relación entre el voltaje de entrada y salida con respecto a las resistencias, que se puede sustituir aún más en la expresión actual. Reorganizar las expresiones ayuda a determinar la impedancia de entrada. Al seleccionar valores de resistencia apropiados, se puede generar una capacitancia efectiva entre el terminal de entrada y tierra, que sea un múltiplo de la capacitancia física. Para evitar que los amplificadores operacionales se saturen, la capacitancia efectiva debe estar limitada por el voltaje de salida invertido. A medida que aumenta la multiplicación de la capacitancia, el voltaje de entrada máximo permitido debe disminuir. Los circuitos multiplicadores de capacitancia como este proporcionan una solución eficiente para generar capacitancias más grandes sin aumentar la capacitancia física.

Ejemplo de diseño: multiplicador de capacitancia

Los circuitos multiplicadores de capacitancia se utilizan en circuitos integrados para producir un múltiplo de una capacitancia física pequeña cuando una capacitancia de alto valor es ...

design-example-capacitance-multiplier-circuit

Education

Educación

JoVE Core

Electrical Engineering

Ingeniería Eléctrica

Unit 1

Unidad 1

AC Circuit Analysis

Análisis de circuitos de corriente alterna (CA)

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

Design Example: Capacitance Multiplier Circuit

capacitance multiplier circuit for larger capacitance

A capacitance multiplier circuit creates a larger effective capacitance from a small physical capacitor. In integrated circuit technology, this approach is useful when a small capacitor is not enough. The circuit can multiply capacitance by as much as 1000, so a 10-pF capacitor can act like a 100-nF capacitor.

The design uses two op-amps. The first op-amp works as a voltage follower, which helps isolate the generated capacitance from the loading caused by the second stage. The second op-amp works as an inverting amplifier.

No current enters the op amp input terminals, so the feedback capacitor carries the input current. Kirchhoff’s Current Law, or KCL, is then used to relate the input and output voltages through the resistances. That relationship can be placed into the current expression and rearranged to find the input impedance.

By choosing the resistance values, the circuit produces an effective capacitance between the input terminal and ground. This effective capacitance is a multiple of the actual capacitor value. The multiplication is limited by the inverted output voltage, so the op-amps do not saturate. As the multiplication factor increases, the maximum input voltage must decrease. Capacitance multiplier circuits provide an efficient way to generate larger capacitances without using a larger physical capacitor.

Capacitance Multiplier Circuit for Larger Capacitance

capacitance-multiplier-circuit-for-larger-capacitance

sinusoidal sources

AC Waveform Basics and Phase

Alternating current, or AC, changes direction and magnitude over time, unlike direct current, or DC, which flows in one direction with constant polarity. AC is the main form of electricity used for modern power transmission and distribution because it can travel long distances efficiently. In homes, power supplies use sinusoidal sources to deliver electricity. A sinusoidal source creates a voltage that rises and falls in a smooth wave-like pattern. This waveform is called a sinusoid, which is...

graphical and analytic representation of sinusoids

graphical-and-analytic-representation-of-sinusoids

Measuring Sinusoid Phase on an Oscilloscope

Measuring sinusoid phase on an oscilloscope helps compare two sinusoidal voltages with the same amplitude and period. An oscilloscope is an instrument used to display and analyze waveforms. The process starts by reading the peak-to-peak value, which is twice the amplitude of the sinusoid. This shows the maximum voltage swing of the waveform. Next, the period and angular frequency are measured. The period is the time for one complete cycle. Angular frequency, often written as omega, is the rate...

phasors

Phasors for AC Circuit Analysis

Phasors are a mathematical tool for analyzing alternating current, or AC, circuits. They represent sinusoids with complex numbers. The phasor magnitude matches the sinusoid amplitude, and the phasor angle shows the phase measured from the positive x-axis. Phasors make AC circuit analysis simpler by removing time from the current and voltage expressions. That lets an AC circuit be treated like its equivalent direct current, or DC, form for calculations. Phasors can also be written in...

phasor arithmetics

Phasor Rules for AC Circuit Analysis

Phasor rules make AC circuit analysis easier by linking sinusoids to their matching phasors. A phasor is a complex-number form of a sinusoidal signal. This connection helps explain how alternating current changes with time. Differentiation and integration work in both the time domain and the phasor domain. If you take the derivative of a sinusoid in time, its phasor is multiplied by jω, where j is the imaginary unit and ω is the angular frequency. If you integrate a sinusoid in time, its...

phasor relationships for circuit elements

phasor-relationships-for-circuit-elements

AC Circuit Phasors: Resistor, Inductor, Capacitor

AC circuit phasors help show how voltage and current behave for resistors, inductors, and capacitors. Phasor representation moves these relationships from the time domain to the frequency domain, which makes AC circuit analysis easier. For a resistor, Ohm's law still applies. The voltage across the resistor and the current through it stay in phase, so their phasors point in the same direction. An inductor works differently because its voltage depends on the rate of change of current. The...

kirchoff's laws using phasors

AC Circuit Rules with Phasor Diagrams

AC circuit analysis uses Kirchhoff's voltage law and Kirchhoff's current law with phasors. In household wiring, AC power from a distribution panel is sent to appliances connected in parallel. These rules help describe how voltage and current behave in sinusoidal steady state. Kirchhoff's voltage law, or KVL, says that the sum of phasor voltages around a closed loop in an AC circuit is zero. The voltages can first be written in the time domain and then changed into phasor form. In phasor...

impedances and admittance

AC Circuit Response: Impedance and Admittance

AC circuit response changes with frequency, and impedance describes how resistors, inductors, and capacitors affect sinusoidal current flow. In phasor form, voltage and current are used to show this behavior in a clear way. Impedance is a key idea in AC circuit analysis because it measures opposition to current in an alternating circuit. These components behave differently in AC than in DC. In DC circuits, inductors act like short circuits and capacitors act like open circuits. In AC circuits,...

impedance combination

Series and Parallel Impedance Rules

Impedance in series and parallel circuits follows the same rules used for resistors. A string of Christmas lights is a simple example. Each bulb represents one impedance element. In a series connection, the current stays the same through every component. This series behavior matches Kirchhoff’s Voltage Law, or KVL. The total impedance in the circuit is the sum of the individual impedances. The source voltage is then divided among the components based on their values. This is the voltage...

node analysis for ac circuits

AC Circuit Node Method in an Angioplasty Model

AC circuit node analysis is used to study an angioplasty system with a catheter turbine. The system helps remove plaque deposits from coronary arteries. Its electrical model is similar to a dual-node RLC circuit driven by a current-controlled voltage source. The analysis begins by collecting the input source voltage, inductance, and capacitance values. These measurements are used to find the driving voltage for the catheter shaft. The circuit is then viewed in the frequency domain, where...

mesh analysis for ac circuits

Impedance Matching with Mesh Currents

Impedance matching in radio communication uses resistor, capacitor, and inductor circuits to help signals move efficiently between a transmitter and a receiver. The circuit must balance the input and output signals before the current in the capacitor can be found. This makes the problem a good example of AC circuit analysis for high school students. The first step is to identify the input voltage and the output signal. The angular frequency is then taken from the time-domain form of the input...

source transformation for ac circuits

AC Source Conversion in Circuit Analysis

AC source conversion is a circuit analysis method used in the frequency domain. It changes a voltage source in series with an impedance into a current source in parallel with the same impedance, or it converts a current source back into a voltage source. The source values must keep the correct relationship during each change. This method helps solve for an unknown voltage in a circuit that includes a current source and components such as resistors, capacitors, and inductors. Each of these...

th&#233venin equivalent circuits

Finding Voltage and Impedance in Circuit A

The household power distribution system can be simplified with Thevenin's theorem. In this system, distribution lines and transformers form the main network. Electrical appliances can be treated as load impedance, which makes the circuit easier to analyze. An AC circuit can be split into two parts, circuit A and circuit B, with a single pair of terminals between them. Circuit A can then be replaced by its Thevenin equivalent circuit. That equivalent has a voltage source in series with an...

norton equivalent circuits

Norton Current in AC Circuit Analysis

Norton’s theorem helps simplify complex AC circuits by replacing a two-terminal linear network with a smaller equivalent circuit. That equivalent circuit uses an impedance in parallel with a constant current source. The method lets students break one complicated circuit into two parts and analyze them more easily. To build the Norton equivalent, the source is replaced by its internal impedance. The result is the Norton impedance, which is the same as the Thévenin impedance. This parallel...

superposition theorem for ac circuits

Analyzing Mixed-Frequency Linear Circuits

Analyzing mixed-frequency linear circuits starts with the principle of superposition. In a linear circuit, the total output from several inputs is the sum of the outputs from each input acting alone. Here, the inputs are the voltages from independent voltage sources and the currents from independent current sources. When one source is kept active, every other independent source is set to zero. A 0-V voltage source becomes a short circuit, and a 0-A current source becomes an open circuit. This...

op amp ac circuits

Analyzing an Op Amp Audio Filter

An op amp audio filter shapes an amplified sound signal by strongly reducing the lower-frequency parts. In this circuit, the focus is on a basic filter setup used after an amplifier in an audio system. The filter uses an operational amplifier in an inverting arrangement with resistors R1 and R2 and a capacitor C1. The analysis starts with a known input signal and asks for the output signal. To solve it, the capacitor impedance is found first. That requires the angular frequency from the...

design example: capacitance multiplier circuit

A capacitance multiplier circuit creates a larger effective capacitance from a small physical capacitor. In integrated circuit technology, this approach is useful when a small capacitor is not enough. The circuit can multiply capacitance by as much as 1000, so a 10-pF capacitor can act like a 100-nF capacitor. The design uses two op-amps. The first op-amp works as a voltage follower, which helps isolate the generated capacitance from the loading caused by the second stage. The second op-amp...

key terms and concepts

Learn how a capacitance multiplier circuit uses two op-amps, KCL, and resistor choices to create a larger effective capacitance from a small capacitor.

Capacitance Multiplier Circuit for Larger Capacitance | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Capacitance Multiplier Circuit for Larger Capacitance

Description

Transcript

Tags