Single Commercially Available IC-Based Electronically Controllable Voltage-Mode First-Order Multifunction Filter with...

Area of Science:

• Electronics
• Analog Signal Processing
• Circuit Design

Background:

• Traditional filter circuits often require numerous components and complex tuning.
• Achieving multifunctionality and electronic control in simple filter designs presents a significant challenge.

Purpose of the Study:

• To design and implement a simple, voltage-mode, first-order filter with multifunction capabilities.
• To demonstrate electronic control over pole frequency and phase response using bias current.
• To enable independent control of gain for low-pass and high-pass functions.

Main Methods:

• Utilized a single LT1228 integrated circuit, two resistors, and one capacitor for the filter design.
• Employed bias current (I) for electronic control of pole frequency and phase response.
• Investigated parasitic effects on filter performance through analysis, simulation, and experimentation.
• Demonstrated filter responses including low-pass (LP), high-pass (HP), inverting all-pass (AP-), and non-inverting all-pass (AP+).

Main Results:

• The proposed filter successfully achieved four distinct filter responses (LP, HP, AP-, AP+) in a single configuration.
• Electronic control of pole frequency and phase response was achieved via bias current adjustment.
• Pass-band voltage gain for LP and HP functions was independently controllable by resistor values.
• Experimental results validated the filter's performance, showing phase shifts from 180 to 0 degrees (AP+) and 0 to -180 degrees (AP-) across a wide frequency range.
• A quadrature oscillator application was successfully designed using the proposed filter.

Conclusions:

• The designed first-order filter offers a simple, versatile, and electronically controllable solution for analog signal processing.
• The use of LT1228 IC simplifies implementation and facilitates laboratory verification.
• The filter's multifunctionality and independent control features make it suitable for various analog circuit applications, including oscillator design.