IMPLEMENTATION OF ANALOG SIGNAL PROCESSING CIRCUITS USING DXCCII

Abstract

Analog signal processing (ASP) is any type of signal processing conducted on continuous analog signals by some analog means as set of continuous values as opposed to the discrete digital Signal Processing (DSP) where the signal processing is carried out by a digital process). DSP suffers of fundamental drawbacks, such as high cost analog-digital conversion, high power consumption and poor performance at high frequencies. To overcome these drawbacks, ASP is preferred. Current-mode (CM) blocks offer advantages over voltage-mode (VM) blocks, such as performance improvement, low power consumption, controlled gain without feedback components, better linearity and improved bandwidth. This gives the motivation to use CM block to implement various ASP applications and to review already existing literatures available using CM blocks. Current conveyor is used as it is a high-performance active element and it ensures high accuracy, wide bandwidth and exceptionally high slew rates combined with low voltage and low power implementations under small or large signal conditions. As compared to op-amp based circuits, the conveyor-based circuits offer a higher gain-bandwidth product, which makes it an ideal choice for modern applications in analog signal processing. Dual-X second-generation current conveyor (DXCCII) is one of the new emerging CM block. In the process, a DXCCII is used which is a modified second-generation current conveyor that provides an extra input terminal. The block DXCCII and its applications have been verified.

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The new topology Current amplifier, Voltage amplifier, Trans-resistance amplifier, Trans conductance Amplifier, Voltage-mode digitally controlled variable gain amplifier (VGA) and current-mode digitally controlled variable gain amplifier (VGA) are proposed and analyzed. To achieve the required gain control range and step, two VGA stages are cascaded. The first stage is coarse gain control while the second stage is fine gain control. The variable gain amplifier (VGA) circuit is thus operating in a coarse and fine arrangement. The novice DXCCII based Programmable Gain Amplifier are proposed and analyzed. It operates in trans-impedance mode i.e. it receives current signal as input and provides voltage as output. It uses four blocks – a current amplifier, digitally controlled trans-impedance amplifier, digitally controlled R-2R ladder network and a voltage buffer. First block amplifies input signals. Second and third blocks of proposed PGA provide control over coarse gain and fine gain through bits (𝐵!−𝐵!) and a total of 60 different gain values are possible through the arrangement. The last block provides output at low impedance.

Another application as a Current-mode all-pass filter using a single dual-X second generation current conveyor (DXCCII) is proposed. The proposed circuit has grounded capacitors and resistors, which is good for IC implementation. The functionality of the proposed circuits is analyzed through SPICE simulation using 0.18µm TSMC technology parameters.