Operational transconductance amplifiers are high gain amplifiers with wide bandwidth. The main advantage of those circuits is their capability to drive high resistive and
capacitive loads at their outputs. Due to such capability, such circuits consume high power.
While in some applications where the current consumption may vary in wide ranges the
self-current of those amplifiers may succeed the load current, thus decreasing the efficiency
coefficient of the designs.
To reduce the intrinsic current consumption without impacting the performance and
functionality, a novel method of an operational transconductance amplifier output stage
design is proposed in this paper. The programmable output stage, in which the output cascade can operate in two different modes using a digital control signal has been designed. As
a result, the parameters of the operational amplifier become more flexible to be tuned and
configured after production. The output impedance, amplifier transconductance, bandwidth
and other main parameters can be easily controlled based on the system state. If the load at
the output enters the power down mode, the impedance of the amplifiers decreases the current and vice versa. The solution has been tested in the modern 14nm FinFet technology
and the achieved results have ensured the capability of the proposed solution to be integrated with modern analog integrated circuits.
This work introduces a flow of digital to analog (DAC) implementation in digital environment of SystemVerilog. Unlike the classical Verilog models, this digital to analog converter behavioral model is analog. Such type of model creation in general is called real number modeling. The DAC model is verified by the HSPICE and SystemVerilog Co-simulations which show its applicability in different register transfer level verification environments. The digital environment with real number modeled DAC runs around 8 times faster than the same environment with SPICE model. At the same time, the output signal’s voltage difference between RNM and SPICE models is less than 2 mV.
Excitonic absorption in monolayer and bilayer graphene systems with opened energy gap in the field of laser radiation is investigated. The obtained value of excitonic binding energy in monolayer is in good agreement with the exact analytical solution. It is shown that the account of all tight binding parameters in bilayer graphene leads to an increase of exciton binding energy.
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