Abstract: The floating immittance emulator is presented in four embodiments in which four new topologies for emulating floating immittance functions are detailed. Each circuit uses three current-feedback operational-amplifiers (CFOAs) and three passive elements. The present topologies can emulate lossless and lossy floating inductances; capacitance, resistance, and inductance multipliers; and frequency-dependent positive and negative resistances.

Abstract: The floating memristor emulator is based on a circuit implementation that uses grounded capacitors and CFOAs in addition to combinations of diodes and resistors to provide the required nonlinearity and time constants. This circuit results in low power consumption, cost reduction and ease of implementation because it avoids the use of multipliers, ADCs and RDACs. The present circuit is used in an FM demodulator, which exploits the frequency-dependence of the memristance. Successful use in the FM demodulator confirmed the functionality of the present floating memristor emulator circuit.

Abstract: The current-feedback operational amplifier-based sinusoidal oscillator circuit includes a pair of CFOAs connected to each other using five resistors and two capacitors. The condition and the frequency of oscillation are fully coupled, and thus none of them can be controlled without disturbing the other. The oscillator circuit provides a high impedance output current and two low impedance output voltages.

Abstract: The logarithmic and exponential function generator for analog signal processing is implemented with CMOS circuits operating in current mode and includes current mirrors connected to a square root function circuit and two current amplifiers. A third current amplifier utilizes a constant current input. The outputs of the current amplifiers are combined to provide the logarithmic and exponential functions.

Abstract: The current-mode folding amplifier is a current-mode saw-tooth folding amplifier having a minimal number of current mirrors in the signal path from input to output. This minimizes the delays imposed by current mirrors on the speed of the amplifier. The amplifier has a full scale delay of 5.9 ns. The operation of the amplifier is verified in simulation using LFoundry 150 nm process in Cadence Tools.

Abstract: The continuous-level memristor emulator is a circuit that uses off-the-shelf components to emulate a memristor. The circuit uses two current-feedback operational-amplifiers (CFOAs) and uses an operational transconductance amplifier (OTA)-based circuit in place of a diode resistive network to provide a continuous level of memristance instead of two binary states. The OTA is forced to work in its nonlinear region by the voltage VDC applied to its positive input terminal. Thus, the transfer function of the OTA-based circuit will be a nonlinear function. Experimental testing shows that the continuous-level memristor emulator is operational as a memristor, and the emulator may be used, e.g., in place of a memristor in a multivibrator circuit.

Abstract: A voltage or current controlled current-feedback operational-amplifier based multivibrator provides oscillation based on two current feedback operational amplifiers, three resistors and one grounded capacitor. The multivibrator can achieve almost constant frequency of oscillation and its duty cycle can be adjusted by a control voltage or a control current. The multivibrator can be used for generating pulse-width modulated signals.

Abstract: The predistortion circuit with concave characteristic is developed from a novel functional model for class-AB solid-state bipolar amplifiers. The model, based on a Fourier sine-series is simple and can provide closed-form expressions for the intermodulation products resulting from exciting the power amplifier by a multi-sinusoidal signal. The special case of a two-tone equal-amplitude signal is considered in detail. The present model can be used to build a database for the intermodulation performance of the class-AB bipolar SSPAs excited by a multi-sinusoidal signal. Using this database, the diode-based predistortion circuit with concave characteristic for linearizing the class-AB solid-state power amplifier is designed.

Abstract: A memristor-based emulator including a memristor circuit for use in digital modulation that includes a first current feedback operational amplifier (CFOA) having multiple terminals in communication with a capacitor Cd and in further communication with a resistor Ri. A second CFOA having multiple terminals is in communication with the first CFOA and is adapted to be in further communication with a voltage vM to provide an input current iM for integration by a capacitor Ci. A nonlinear resistor is in communication with the second CFOA. A third CFOA having multiple terminals is in communication with the nonlinear resistor and is in further communication with the first CFOA and a resistor Rd. The third CFOA and the resistor Rd act as an inverting amplifier associated with the nonlinear resistor to increase a current gain to increase a difference between ON and OFF values of a resistance of a realized memristor.

Abstract: The programmable CMOS-based nonlinear function synthesizer is a circuit that assumes that the required nonlinear function can be approximated by the summation of hyperbolic tangent (tan h) functions with different arguments. Each term of the tan h function expansion is realized using a current-controlled current-conveyor (CCCCII), or an operational transconductance amplifier (OTA)) with a different bias current. The output weighted currents of these CCCCIIs or OTAs are algebraically added to produce the output current. The present circuit can be easily integrated, extended to include higher order terms of the tan h-function expansion and programmed to generate arbitrary hard nonlinear functions. By controlling the bias current and without changing the aspect ratios of the transistors, various tan h functions with different arguments from the same topology can be obtained.

Abstract: A current controlled operational transconductance amplifier based sinusoidal oscillator circuit that provides oscillation based on the transconductance and parasitic capacitance of the operational transconductance amplifier without externally connected capacitances. The oscillation frequency is adjusted through a variable current source or a variable resistor with a DC voltage source.

Abstract: A current-feedback operational-amplifier Based Relaxation oscillator provides oscillation based on a current feedback operation amplifier and two external resistors which exhibit a low output impedance terminal. This current-feedback operational-amplifier Based oscillator is used as a component for a capacitive, resistive and capacitive-resistive sensor electronic interfacing circuit.

Abstract: A programmable sinusoidal oscillator circuit is a sinusoidal oscillator circuit that includes a current-feedback operational-amplifier (CFOA) operably connected to two operational transconductance amplifiers (OTAs), two capacitors and a resistor. The programmable sinusoidal oscillator circuit enjoys electronic orthogonal tuning of the frequency and the condition of oscillation by adjusting the biasing currents (voltages) of the OTAs, as well as providing a low output impedance.

Abstract: The nonlinear systems measurement system includes two signal generators generating different sinusoidal frequencies. A spectrum analyzer measures all signals. A single software program synchronizes the instruments. The fetched measurements are kept in data registers in correct sequence for feeding into two curve fitting routines. The sinusoidal signals are fed to a suitable combiner for the expected frequencies and dynamic range of the UUT. The combined signal is applied to the UUT. Via a software-controlled single-pole, triple-throw RF switch, the amplitude of the UUT output and the two input signals are measured at every power step as amplitude I1 and amplitude I2. The amplitude of the output component from the UUT at f1-f2 is measured as IMD2 and the output component at 2f1-f2 is measured as IMD3. The measured I1 and IMD2 are fed to the curve-fitting routine 1, yielding r1. The measured I2 and IMD3 are fed to curve-fitting routine 2, yielding r2.

Abstract: The current-feedback operational amplifier-based sinusoidal oscillator provides oscillations based on a single external resistor and a single external capacitor, which exploit the internal parasitic components of the CFOA. The external resistor and external capacitor are passive, externally connected, and grounded.

Abstract: The CMOS programmable non-linear function synthesizer utilizes CMOS current-mode electronics to provide synthesis of arbitrary analog functions. The circuit approximates a seventh-order Taylor series expansion to synthesize an arbitrary nonlinear function. Each term of the Taylor series expansion is realized using a current-mode basic building block, and the output weighted currents of these basic building blocks are algebraically added in addition to a DC current, if needed. The CMOS current mode electronic circuit can be easily integrated, extended to include higher order terms of the Taylor series, and programmed to generate arbitrary nonlinear functions.

Abstract: The CMOS programmable non-linear function synthesizer utilizes CMOS current-mode electronics to provide synthesis of arbitrary analog functions. The circuit approximates a seventh-order Taylor series expansion to synthesize an arbitrary nonlinear function. Each term of the Taylor series expansion is realized using a current-mode basic building block, and the output weighted currents of these basic building blocks are algebraically added in addition to a DC current, if needed. The CMOS current mode electronic circuit can be easily integrated, extended to include higher order terms of the Taylor series, and programmed to generate arbitrary nonlinear functions.

Abstract: The arbitrary power law function generator uses an equal number of exponential and logarithmic circuits, e.g., two exponential and two logarithmic circuits, which are current-mode, current-controlled circuits that provide positive, negative, integer, or non-integer powers independent of temperature. Moreover, the circuit can operate from a DC power supply as low as ±1.5V. SPICE simulation results using practical bipolar junction transistor (BM parameters are included to confirm the feasibility of the function generator.

Abstract: The balanced output signal generator uses four interconnected plus-type second-generation current conveyors, a couple of load resistors and a single input resistor that can provide both current- and voltage-mode outputs. No matching conditions are required.

Abstract: The balanced output signal generator uses four interconnected plus-type second-generation current conveyors, a couple of load resistors and a single input resistor that can provide both current- and voltage-mode outputs. No matching conditions are required.