Four Unity/Variable Gain First-Order Cascaded Voltage-Mode All-Pass Filters and Their Fully Uncoupled Quadrature...

Area of Science:

• Electronics Engineering
• Analog Circuit Design
• Integrated Circuit Design

Background:

• All-pass filters (APFs) are crucial for phase shifting in signal processing.
• Existing APF designs often lack high input impedance, necessitating buffers for cascading.
• Differential voltage current conveyors (DVCCs) offer versatile building blocks for analog circuits.

Purpose of the Study:

• To propose four new designs for first-order voltage-mode (VM) all-pass filter (APF) circuits.
• To achieve high input impedance and variable gain control in the proposed APF designs.
• To demonstrate the applicability of these APFs in integrated circuits (ICs) and cascaded filter structures.

Main Methods:

• Design of four first-order VM-APF circuits utilizing two single-output positive DVCCs.
• Incorporation of grounded capacitors and resistors for simplified implementation.
• Addition of resistors to achieve variable gain control in two of the designs.
• Validation through PSpice simulations and experimental construction using AD8130 and AD844 ICs.

Main Results:

• The proposed APFs exhibit high input impedance, allowing direct cascading without buffers.
• Experimental results confirm the theoretical performance of the APF and a cascaded oscillator circuit.
• Measured power dissipation is 0.6 W, input 1-dB compression point is ~19 dB, and THD is <0.67% at 2.5 Vpp.
• Figures of merit range from 496.42 × 10³ to 628.2 × 10³.

Conclusions:

• The presented four first-order VM-APF designs are suitable for IC implementation due to grounded passive components.
• The high input impedance facilitates the creation of higher-order filters through cascading.
• The designs offer a practical solution for analog signal processing applications requiring precise phase control.