1kH Synthetic Inductor

Description: Inductors can be easily simulated using operational amplifiers. The circuit presented is designed to achieve an inductance of 1000 H (one thousand Henry) with effective damping. This configuration enables the construction of a resonant circuit with a center frequency of less than 1 Hz. The slow response time permits the use of standard measuring instruments to analyze the circuit in real-time. Additionally, the circuit can be incorporated into filter designs. Opamp1 functions as an integrator, while Opamp2 serves as a difference amplifier. The output voltage of Opamp2 corresponds to the voltage drop across R1 and P1, which is proportional to the output current. This voltage is then differentiated by Opamp1, C1, and R2. The overall effect is that the circuit simulates an inductor. P1 facilitates the adjustment of the inductance value, while P2 allows for the modification of the Q factor of the coil by changing the symmetry of the difference amplifier, thereby influencing the stability of the circuit.

The circuit utilizes two operational amplifiers (Opamps) to emulate the behavior of an inductor, which is particularly useful in applications where traditional inductors may be impractical due to size, weight, or frequency limitations. The first operational amplifier (Opamp1) operates as an integrator, which is essential for creating a voltage that is proportional to the integral of the input current. This function is achieved by connecting a capacitor (C1) in feedback with a resistor (R2), allowing the circuit to accumulate charge over time, thereby simulating inductive behavior.

The second operational amplifier (Opamp2) is configured as a difference amplifier. It measures the voltage drop across a resistor (R1) and a potentiometer (P1), which serves as a variable resistor to adjust the circuit's inductance. The output of Opamp2 reflects the current flowing through the circuit, which is critical for maintaining the desired inductive response.

The inclusion of potentiometer P1 provides the flexibility to fine-tune the inductance, enabling the circuit to adapt to various applications. Additionally, potentiometer P2 adjusts the Q factor, which is a measure of the circuit's quality and stability. By altering the symmetry of the difference amplifier, P2 influences the damping characteristics of the circuit, allowing for optimization based on specific requirements.

This circuit design is particularly advantageous in low-frequency applications where conventional inductors may not perform adequately. The ability to utilize standard measuring instruments for real-time analysis enhances the practicality of this design in experimental and educational settings, facilitating a deeper understanding of inductive behavior in circuits. Overall, the operational amplifier-based inductor simulation provides a versatile and effective solution for various electronic applications.Inductors can be mimicked quite easily using operational amplifiers. The circuit shown here was developed to have an inductance of 1000 H (say, one thousand Henry) with good damping. Using this design you can build a resonant circuit with a center frequency of less than 1 Hz. The slow behavior allows you to use conventional measuring instruments t o investigate the circuit in real time. The circuit can also be used as part of alter design. Opamp1 operates as an Integrator, Opamp2 as a difference amplifier. The output voltage of Opamp2 is equal to the voltage drop across R1 and P1, which is proportional to the output current. This voltage is differentiated by Opamp1, C1 and R2. The net effect is that the circuit behaves as an inductor. P1 allows adjustment of the inductance value. P2 allows adjustment of the Q factor of the coil by altering the symmetry of the difference amplifier and with it the stability of the circuit.