Voltage Feedback Op-amps Research Articles

Design Of High-Speed Low Voltage Operational Amplifier

Background: The Operational amplifier (op-amp) is the building block of linear integrated electronics, therefore proposing newer design models with improved parameters is an essential landmark in the electronics industry in the hunt for a faster and more efficient design. Objective: To attain high speed and low power supply, the authors designed an op-amp using three different techniques. Initially compensating network was designed and simulated but the resultant output voltage saturates in inverting and non-inverting modes. Methods: Voltage feedback op-amp (VFOA) and current feedback op-amp (CFOA) were proposed to achieve the target. The authors have successfully designed the circuit, but the power dissipated is less and Common Mode Rejection Ratio (CMRR) is high in CFOA in comparison to VFOA. Results: The results are simulated for three different configurations and inverting configuration results in remarkable results in comparison to a non-inverting and differential amplifier. Inverting configuration using VFOA results in 91.22dB, and 0.0131W CMRR and power dissipation, respectively, while that of CFOA results in 97.34dB, and 0.0129W CMRR, and power dissipation, respectively. Conclusion: 1.6% improvement in CMRR and a 26.8% improvement in power dissipated for the proposed CMOS CFOA in comparison to the proposed VFOA. All the validations are done by plotting the bode plot and Nyquist plot.

Behavioral Modeling Technique for TID Degradation of Complex Analog Circuits

A behavioral modeling technique has been developed for creating TID-aware behavioral models of voltage feedback op-amps without the creation of an underlying SPICE micro-model. The model accurately predicts the TID response of board-level designs with a 79X increase in simulation speed when compared to the SPICE model for the example application of a Schmitt trigger oscillator. This behavioral model permits the analysis of op amp characteristic sensitivity on circuit level behaviors. This type of sensitivity analysis can be particularly useful for determining which portion of a circuit is most affected by TID and where to more effectively harden a system against TID degradation.

Maximum oscillation frequencies and ft sensitivities of two groups of single-VFOA active-RC oscillators

Two groups of three active-RC oscillators that use a single voltage feedback op amp (VFOA) are compared. Linear analysis using a first-order VFOA model shows that all six oscillators have the same maximum oscillation frequency (OF) of 16.67% of the op amp gain-bandwidth product (GBP), despite the fact that based on an ideal VFOA the gain required in the oscillator amplifier section is 3 for one group and 1.5 for the other.Sensitivity of OF to op amp GBP is found to be the same for both groups. Simulation results using a nonlinear VFOA macromodel give good agreement with linear analysis.

Using High Frequency Operational Amplifiers for Low Noise Design

In this paper we present a comprehensive noise and stability analysis of both the current feedback and the voltage feedback op-amp when connected as transimpedance amplifiers with capacitive current sources. It is generally assumed that the current feedback op-amp is noisier than the voltage feedback op-amp; we show how external component values play an important role in determining the total equivalent input noise current spectral density and show that the voltage feedback op-amp may, in certain cases, be noisier than the current feedback op-amp. Both amplifier types are compared in terms of stability, noise and bandwidth; we find that the current feedback op-amp is particularly suited for operation as a transimpedance amplifier. Theoretical analysis is confirmed by simulations of equivalent circuits of the current feedback op-amp and the voltage feedback op-amp, and simulations of the macro models of two high performance commercially available op-amps, namely the Elantec EL2260 current feedback op-amp and the Elantec EL2244 voltage feedback op-amp.

Design of a low EMI susceptibility CMOS transimpedance operational amplifier

In this work we analyze the effects of electromagnetic-induced interferences conveyed at the input of a transimpedance CMOS operational amplifier. In particular, it will be highlighted that transimpedance amplifiers natural exhibit a lower EMI susceptibility compared to common voltage-feedback opamps. Moreover, it will be shown through simulations that a careful circuit design can lead to opamps with a practically vanishing EMI susceptibility.