Littérature scientifique sur le sujet « OPERATIONAL TRANS-RESISTANCE AMPLIFIER »

In this paper, we present the design of a versatile general multiplier-divider cell by using the Operational Trans-resistance Amplifier (OTRA) and MOSFETs operating in the linear region. The design and the basic operation of this block is verified. Other operations can also be realized by simply choosing the inputs of the signals at the different terminals. These operations include square root operation, scalar vector multiplier and modulation to name a few. The new cell is reconfigurable and can be programmed by DC voltages. The resulting circuits are simulated by 0.18 m CMOS process through PSPICE. These simulation results verify the versatile operation of this cell.

Two new electronic tuning current-mode square-wave generators are introduced in the ensuing paper. In the first proposed square-wave generator circuit, one Operational Trans-resistance Amplifier (OTRA) and two passive components are involved, along with two NMOS depletion mode transistors. This circuit generates a square-wave with almost equal and fixed duty cycles. The second proposed circuit is able to control both on-duty and off-duty cycles independently with the help of two passive components, two NMOS depletion mode transistors, and two diodes connected to the circuit. The frequency of the proposed circuits can be adjusted with the passive components connected to the circuit. Moreover, electronic tuning can also be achieved with the proposed circuits. The measured results that are included in the paper show the linear variation of a time period as compared with existing OTRA based square waveform generator. The performance of the proposed circuits is examined while using SPICE models. These circuits are built on a laboratory breadboard using commercially available Current Feedback Operational Amplifier (AD844 AN) and passive components are connected externally and tested for square waveform generation. The obtained results demonstrate good agreement with the theoretical values.

M.TECH
With the evolution of submicron technologies such as 0.18 micron and 0.13 micron, the supply voltages have been reduced to 1.5 volts and lower. This makes it difficult to design a voltage mode CMOS circuit with high linearity and wide dynamic range. Also as signal processing extends to higher frequencies, the traditional design methods based on voltage operational amps are no longer adequate. To overcome these problems circuits operating in current mode are preferred. Various analog building blocks operating in the current mode are available. Operational Trans-Resistance Amplifier (OTRA) is one of them. OTRA is a current controlled voltage source. Both its input and output terminals are characterized by low impedance, therefore eliminating response limitations incurred by capacitive time constants. Its bandwidth is independent of closed loop voltage gain. Thus using the OTRA as the active building block various signal processing and generating circuits can be realized with more flexibility in controlling the frequencies of waveforms. The Operational Trans-Resistance Amplifier (OTRA) is though not available as a single IC but various CMOS circuit realizations are available in literature and can also be implemented using two standard CFOAs. One such CFOA that can be used is the commercially available AD844AN IC 5 manufactured by Analog Devices Inc., US. The AD844AN has current feedback architecture. In this project Operational Trans-Resistance Amplifier (OTRA) based different analog signal processing and generating circuits such as Filters, Multiphase Sinusoidal Oscillators (MSO), Voltage Controlled Oscillator (VCO) and LC oscillator based on active realization of inductor have been realized. The theoretical results have been verified through PSPICE simulations and experimental work by assembling practical circuits of the above and testing them to give near theoretical results. For practical circuits the OTRA has been realized using the AD844AN CFOA ICs manufactured by Analog Devices.