Soliman A. Mahmoud

Low-Voltage digitally controlled fully differential current conveyor

Design and simulation of a digitally controlled CMOS fully differential current conveyor (DCFDCC) is presented. A novel current division network (CDN) is used to provide the digital control of the current gain between terminals X and Z of this DCFDCC. The proposed DCFDCC operates under low supply voltage of /spl plusmn/1.5 V. The realization of the DCFDCC using the new CDN is presented by two approaches. First approach has linearly proportional current gain with the digitally controlled parameter of the CDN, while the second approach exhibits current gain between terminals X and Z greater than, or equal to, one. Applications of the DCFDCC in realizing second order universal active filter and variable gain amplifier are given. PSPICE simulation confirms the performance of the proposed blocks and its applications.

New MOS-C biquad filter using the current feedback operational amplifier

A new MOS-C bandpass-low-pass filter using the current feedback operational amplifier (CFOA) is presented. The filter employs two CFOAs, eight MOS transistors operating in the nonsaturation region, and two grounded capacitors. The proposed MOS-C filter has the advantage of independent control of Q and /spl omega//sub 0/. PSpice simulation results for the proposed filter are given.

CMOS voltage controlled floating resistor

A new CMOS floating linear resistor circuit with a wide linearity range is proposed. The circuit employs 14 transistors all operating in the saturation region. A modified circuit which employs one more transistor, such that it is threshold voltage independent, is also given. PSPICE simulations taking into account the second order effects due to the channel length modulation and mobility degradation are given.

The differential difference operational floating amplifier: a new block for analog signal processing in MOS technology

A wide-range differential difference operational floating amplifier (DDOFA) is introduced. The DDOFA is a new block useful for continuous-time analog signal processing. The DDOFA is realized using a differential difference transconductor with large signal handling capability and a single input differential output current op-amp. The DDOFA forces two differential voltages to the same value and provides two balanced output currents. This brief presents a CMOS realization of the DDOFA, and some of its applications are provided, such as a voltage-to-current converter, MOS-grounded and floating resistors, a MOS multiplier/divider cell, a differential integrator, a continuous-time MOS-C filter, a MOS-C current oscillator, and a MOS-C floating inductor. Simulation results for the DDOFA circuit and its applications are given.

DIGITALLY CONTROLLED CMOS BALANCED OUTPUT TRANSCONDUCTOR AND APPLICATION TO VARIABLE GAIN AMPLIFIER AND GM-C FILTER ON FIELD PROGRAMMABLE ANALOG ARRAY

A digitally controlled balanced output transconductor (DCBOTA) is proposed and analyzed. The proposed DCBOTA is based on the BOTA given in Ref. 1 and MOS switches. The DCBOTA transconductance is tunable in a range of 2n-1 times using n bits control word. The proposed DCBOTA is simulated using CMOS 0.35 μm technology and the results have shown the feasibility of the proposed DCBOTA. The simulation results show that the DCBOTA has a transconductance tuning range from 20 μA/V to 140 μA/V using 3 bits control word and a 3-dB bandwidth larger than 80 MHz. A general configurable analog block (CAB) based on the proposed DCBOTA, capacitor array and MOS switches, is also presented. A collection of the CABs, fully differential buffers (FDBUFs), and their interconnection to construct a field programmable analog array (FPAA) is introduced. The DCBOTA is also used to realize a wide band digitally controlled variable gain amplifier (DCVGA) and six-order lowpass filter with variable gain and tunable cutoff frequency from 1 MHz to 7 MHz.

Low Voltage Rail to Rail CMOS Current Feedback Operational Amplifier and its Applications for Analog VLSI

This paper presents a new CMOS current feedback operational amplifier (CFOA) with rail to rail swing capability at all terminals. The circuit operates as a class AB for lower power consumption. Besides operating at low supply voltages of ±1.5 V, the proposed CFOA has a standby current of 200 μA. The proposed CFOA circuit is thus a versatile building block for low voltage low power applications. The applications of the CFOA to realize a transconductor/multiplier cell, MOS-C differential integrator, MOS-C bandpass filter and MOS-C oscillator are given. PSpice simulations based on 1.2 μm level three parameters obtained from MOSIS are given.

FULLY PROGRAMMABLE UNIVERSAL FILTER WITH INDEPENDENT GAIN-ω0-Q CONTROL BASED ON NEW DIGITALLY PROGRAMMABLE CMOS CCII

A fully programmable second-order universal filter with independently controllable characteristics is presented in this paper. The proposed filter is based on a new ± 0.75 V second-generation current conveyor with digitally programmable current gain. The input stage of the current conveyor is realized using two complementary MOS differential pairs to ensure rail-to-rail operation. The output stage consists of a Class-AB CMOS push-pull network, which guarantees high current driving capability with a 47.2 μA standby current. The digital programmability of the current conveyor, based on transistor arrays and MOS switches, provides variable current gain using a digital code-word. Two approaches for implementing current conveyors with programmable current gain either greater or less than one are described. The fully programmable universal filter and the proposed digitally programmable current conveyor circuits are simulated using PSPICE with 0.25 μm CMOS technology from MOSIS.

New CMOS fully differential difference transconductors and application to fully differential filters suitable for VLSI

New CMOS voltage controlled fully differential difference transconductors (FDDT) are presented. The basic structure of the proposed transconductors is based on the current linearization of basic MOS cells in different configurations consisting from two or four NMOS matched transistors operating in the saturation region. The proposed transconductors are used to design fully differential second order lowpass, bandpass and highpass filters suitable for VLSI. PSpice simulation results for the proposed fully differential difference transconductors and their filter applications indicating the linearity range and verifying the analytical results are also given.

Novel MOS-C oscillators using the current feedback op-amp

Three new MOS-C oscillators using the current feedback op-amp are presented. The proposed oscillators have the advantage of independent control of the oscillation frequency and the condition of oscillation. Two of the proposed MOS-C oscillators provide two outputs in phase quadrature. The third proposed oscillator provides two outputs in the balanced form. PSpice simulation results for the proposed oscillators are given.

New CMOS fully differential current conveyor and its application in realizing sixth order complex filter

A sixth order complex filter based on the usage of a newly proposed fully differential current conveyor (FDCC) is presented in this paper. The FDCC new structure is based on usage of differential difference operational floating amplifier (DDOFA) [1] and floating current source circuits [2]. The block is realized using 0.25µm CMOS technology under ±1.5V power supply. PSPICE simulation for the FDCC is done for testing the block. The simulation shows that the FDCC has ±0.5V input dynamic range, 95MHz 3-dB frequency at output terminal under 10KΩ load and 7.21mW total power dissipation. The FDCC is used to realize first order complex filter with 1 MHz center frequency and second order complex filter at 500 KHz center frequency. Finally; using cascading technique, a sixth order complex filter at 500 KHz center frequency is proposed. The proposed filter is suitable for applications like Bluetooth receivers. All the proposed filter circuits are simulated using ADS simulator.