Abdullah T. Tola

Low-component count BJT technology-based currentcontrolled tunable resistors and their applications

In this study, low-power and low-component count grounded and floating current-controlled tunable resistors are proposed. The validity of the proposed resistor circuits is demonstrated in two applications, second-order band-pass filter and negative inductor simulator circuit. To carry out the performance of the circuits, all the designed circuits are simulated through SPICE program by using real transistor models. Also, experimental results are included to confirm the theory. It is important to note that all the introduced circuit parameters and resistor values can be changed electronically by adjusting the values of dc control current sources only. Approximately four decades tunability range (from 34 Ω to 285 kΩ) and about 10 MHz bandwidth for the tunable resistors are achieved. In this tunability range, linear relationships between terminal currents and voltages are successfully obtained.

Electronically Tunable Square-Root Domain Filter Circuit

In this paper, electronically tunable square root domain low pass and band pass filter is designed by using state space synthesis procedure. A dummy DC input is added to state space equations in order to realize the filter. Natural frequency of the proposed filter could be tuned by varying the currents of the current sources. The designed filter is simulated in PSpice using TSMC 0.35 ¿m CMOS technology parameters. By varying the values of the current sources, the natural frequencies is swept for 2.95 MHz-8.31 MHz and 3.67 MHz-8.46 MHz, for band pass and low pass filters respectively. Also THD and noise analysis are simulated. The obtained simulation results are given.

Two lossy integrator loop based current-mode electronically tunable universal filter employing only grounded capacitors

Abstract In this paper, a novel single-input and multiple-output second-order current-mode universal filter is proposed where lossy integrator blocks, scaling blocks and summing blocks are employed. The proposed filter can simultaneously generate all the five universal filter responses namely; low-pass, high-pass, band-pass, notch and all-pass responses without requiring any critical passive component matching conditions. It uses only two grounded capacitors as passive components and BJTs as active elements; thus, it can be classified as an active-C filter. Both resonance frequency and quality factor of the proposed filter can be tuned electronically. Approximately 1.5 decades adjustable input frequency range for all the universal filter responses and high quality factor for band-pass response are obtained. Obtained PSpice simulation results confirm the theoretical design. Non-ideality and Monte Carlo analyses are also given. A practical realization of the single lossy integrator is accomplished. All the presented results are discussed.

A systematic class AB state space synthesis method based on MOSFET square law and translinear square‐root cells

SUMMARY A new state space Class AB synthesis method for the design of square-root domain filter based on the MOSFET square law is proposed in this study. Those circuits designed by the proposed Class AB systematic synthesis method have the advantages of Class AB circuit structure and translinear circuits. Two alternative design procedures were suggested for designing new circuits. Proposed synthesis technique is applied for designing of a first order all-pass filter and a third order low-pass filter. Circuits are simulated in PSpice using 0.35 µm CMOS technology parameters. Time domain and frequency domain analysis of the proposed filters are performed, and simulation results of those are also presented. The simulation results show that the proposed synthesis technique is appropriate for the design of different types of filters and has the advantages of Class AB circuit structure. Copyright

High frequency log domain all pass filter based on KHN topology

In this study, a current mode Log domain Class AB differential type all pass filter based on KHN structure has been synthesized by using the state space method and by adopting translinear circuits for the first time. The proposed circuit is synthesized for high frequency applications, i.e. around 100 MHz. Varying the values of the current sources of the circuit, the natural frequency of the filter can be tuned electronically. The circuit is simulated in PSpice by using both idealized and real transistors that are suitable for high frequency operations. Simulations showed that amplitude response of the system remains almost constant for 6 decades between 10 kHz and 10 GHz. Moreover, natural frequency of the filter can be set by electronically changing the source currents between 2 mA and 7 mA. In addition to these simulations, THD and noise analysis are carried out. The obtained results are given.

By Using Darlington Topology Improvement of In-Band Gain for the Log Domain Filters

By using Darlington topology, an alternative circuit is proposed to overcome the in-band gain problem for the log domain circuits. This idea is applied to a third order elliptic filter synthesized in the log domain. Simulations are performed in order to compare the performances of ideal transistors with infinite forward gain, CBIC-R transistors and CBIC-R transistors connected in Darlington topology. The AC response of the Darlington connected transistors gives better performance in terms of in-band gain. THD and noise performances are also investigated. In addition, the circuit is driven by a signal at the filters corner frequency, i.e. f=100 kHz, for the time domain analysis. The results are discussed

Second order Class A log domain all pass filter design employing lossy integrators

In this study, a new Class A second order log domain all pass filter is designed by using lossy integrators. An all pass filter has unity gain at all frequencies. It also shifts phase at desired value at the given frequency of the input signal. The proposed filter circuit design is based on Kerwin-Huelsman-Newcomb (KHN) block diagram by using lossy integrators. The circuit is synthesized by using state space synthesis method and the translinear principle. The natural frequency f0 of the circuit is electronically tunable by varying amplitudes of the current sources. PSpice simulation results are given to verify the theoretical analysis. The simulations are performed with both ideal transistor models and AT&T CBIC-R type real transistor models.

The synthesis of second order programmable and electronically tunable universal filter in the log domain

In this paper, a low voltage and electronically tunable Class AB differential type universal filter is synthesized in the log domain. The high pass, band pass and low pass frequency characteristics can be obtained by programming some current sources. The filter’s Q quality factor and natural frequency could be tuned by varying the currents of the current sources. The second order log domain filter is synthesized in the state space. The proposed universal filter with 1.5 V voltage source is simulated in PSpice for ideal and CBIC-R type transistors. By varying the values of the current sources, the natural frequency is swept for 50kHz-5MHz and Q quality factor is tuned for 0.707-5 electronically. The obtained simulation results are given.

Design of current mode, low voltage and electronically tunable class ab differantial type khn filter in the log domain

In this paper, a current mode, low voltage and electronically tunable Class AB differential type KHN filter is synthesized in the log domain. The filter’s Q quality factor and natural frequency could be tuned by varying the currents of the current sources. The signal in the filter is processed by integrators synthesized in the state space and arithmetic blocks. The proposed universal filter with 1.5 V voltage source is simulated in PSpice for ideal and CBIC-R type transistors. By varying the values of the current sources, the natural frequency is swept for 50kHz-5MHz and Q quality factor is tuned for 0.707-5 electronically. The obtained simulation results are given. 1. Giris

State-space synthesis of a first-order differential class-AB log-domain allpass filter

A first-order differential type class-AB log-domain filter is proposed. It is systematically derived using the state-space synthesis procedure. To the best knowledge of the authors, the filter is the first log-domain first-order allpass filter in the literature. PSPICE simulations are performed using both, Bipolar Junction Transistors (BJT) and ideal devices to confirm the theoretical analysis. The small deviations in the gain and phase response from theoretical values are caused by the non-idealities of the BJT such as finite-beta, non-zero ohmic junction resistances, Early voltages. 1. Giriş Translinear filtreler, genlik uygunlaştırıcı akım modlu filtreler ya da üstel durum-uzay filtreleri olarak da adlandırılan logaritmik ortam filtreleri, düşük gerilim, düşük güç tüketimi, düşük gürültü, yüksek frekans uygulamalarında ve elektronik olarak kesim frekansının ayarlanabilir olması, tümdevre teknolojisine uygunluk gibi özelliklerinden dolayı son yıllarda literatürde büyük bir ilgi odağı olmaktadır. Logaritmik ortam filtrelerinde temel yaklaşım, BJT’nin üstel I-V karakteristiğine dayanmaktadır. Logaritmik ortam filtrelerinde, giriş ile çıkış arasında lineer bir ilişki olmasına karşın, işaretin işlendiği ortam tümüyle non-lineer bir ortamdır. Filtre gerçekleştirme yöntemleri bakımından da diğer filtre tekniklerine göre büyük avantajlar sağlamaktadır. Filtre fonksiyonunu gerçekleştirmek için sadece kapasite ve transistör kullanımı yeterli olmaktadır Logaritmik ortam filtre düşüncesi ilk defa Adams tarafından 1979 yılında ortaya atılmıştır [1]. Adams yaptığı çalışmada, diyot, kondansatör, akım kaynağı ve op/amp kullanarak birinci dereceden alçak geçiren logaritmik ortam filtresi tasarlamıştır. Adams, devresinde ilkönce giriş işaretinin logaritmasını almış, filtre işlemini gerçekleştirdikten sonra da çıkışta giriş fonksiyonunun tersi olan üstel bir fonksiyon uygulamıştır [1]. Adams’tan sonra 1990 yılında birbirinden bağımsız farklı iki çalışma yapılmış bu çalışmalar daha sonra logaritmik ortam filtreleri ile ilintilendirilmiştir. Tsividis ve Seevinck tarafından yapılan bu çalışmalar, logaritmik ortam filtrelerinin en önemli özelliklerinden biri olan işaretin sıkıştırılıp genişletilmesi ile ilgilidir [2],[3]. Logaritmik ortam filtrelerde dönüm noktası 1993 yılı olmuştur. Çünkü, Adams’tan sonra ilgi görmeyen logaritmik ortam düşüncesi Frey’in çalışması ile beraber bir anda ilgi odağı olmuştur [4]. Frey, sistematik bir sentez metodu geliştirerek BJT, akım kaynağı ve kondansatörlerden oluşan logaritmik ortam filtresini sunmuştur. Frey tasarım metodu olarak durum-uzay sentez metodunu kullanmıştır. Yapılan bu çalışmadan sonra logaritmik ortam filtreleri literatürde bir anda ilgi odağı olmuş ve ard arda bir çok çalışma hızlı bir şekilde yapılmıştır. AB sınıfı devre mantığı yükselteç devrelerinde kullanılmaktaydı. AB sınıfı filtre düşüncesi ise ilk defa Seevinck tarafından sunulmuştur [3]. Frey, Seevinck tarafından ortaya atılan AB sınıfı filtre yapısını logaritmik ortama taşımıştır [5]. Daha sonra Frey ve Tola tarafından AB sınıfı fark alıcı filtrelere ait genel bir teori ortaya konulmuştur [6]. Fark alıcı AB sınıfı filtreler sağ ve sol olmak üzere iki parçadan oluşmaktadır. Bu yüzden giriş işaretinin de ikiye ayrılması gerekmektedir. Giriş işaretini ikiye ayırmak için de farklı devreler geliştirilmiştir. İşaretin çıkışı sol ve sağ olmak üzere ikiye ayrılmakta ve bunların farkı alınarak çıkış işareti elde edilmektedir [6],[7]. Yapılan bu çalışmada da analog işaret işleme uygulamalarının en önemli blok yapılarından biri olan birinci 0-7803-9238-8/05/