The Design And Research Of High Linearity CDTA And Its Current Mode Filter

At the beginning of the 21st century, with the rapid development of integrated electronic circuits, people began looking for a circuit with excellent performance in terms of speed, dynamic range and power and so on, so current mode circuits came into being. The current-mode filters based on current differential transconductance amplifier (CDTA) have a low supply voltage, high frequency, large linear operating range, low power consumption, simple circuit configuration and so on.This paper aims to study design theory, design method and implementation circuit of the continuous-time analog filters based on CDTA. Firstly, the basic design principles of continuous-time filter was analyzed, and then different types of filters and implementation method of filters are summed up. Then based on research and analysis of the current mode circuit and the current differential transconductance amplifier, a new type of CDTA, a biquad filter and a high order active filter with tunable gain based on proposed CDTA are realized. At last, layout design and verification of the proposed CDTA and filters are presented. The main innovations and works about this paper are as follows:1. A new low-voltage high-linearity CDTA is presented. The circuit is composed of two basic modules:the current differential circuit and transconductance amplifier with an adaptive bias current source. The circuit theoretical analysis and simulation results show that the proposed new CDTA has a low input impedance current, supply voltage, high output impedance, high linearity and wideband tunable transconductance characteristics.2. A new biquad filter consisting of three CDTAs and two grounded capacitors is presented. A circuit configuration with three-input single-output is very simple, and it can achieve five kinds of filtering function including low-pass, band-pass, high-pass, band-stop and all-pass by setting a reasonable current access mode and the number of access.3. For the shortcomings of existing gain-untunable transconductance amplifier based on CDTA, a three-input, single-output current-mode gain-tunable higher order low pass filter is presented. Natural frequency and quality factor of the proposed filter circuit are independently adjustable. The higher the order of the filter, the wider the adjustable gain range.4. Layout design and verification of the proposed CDTA, the new biquad filter and gain-tunable higher order low pass filter were carried out.