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Signal Conditioning and Output Devices
Published in Francis S. Tse, Ivan E. Morse, Measurement and Instrumentation in Engineering, 2018
The basic inverting amplifier is shown in Fig. 6-4a. The input voltage V1 and the output Vo are of opposite signs. This is an advantage when a sign change is needed. The resistor Rf is the feedback element. Since terminal b is grounded, terminal a becomes a virtual ground, that is, Va ≃ Vb = 0. A virtual ground is essentially at the ground potential but is not directly connected to ground. Summing the currents at node a and using Ohm’s law, we get () I1=If+IawhereIa≃0V1−VaR1=Va−V0Rf+0whereVa≃0 () VoV1=−RfR1
V
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
vibration damper vibration damper any of a number of devices mounted on a power line to reduce vibrations caused by wind. vibrational transition transition between vibrational states of a molecule. video (1) representation of moving images for storage and processing. Often used interchangeably with television. In particular, "video signal" and "television signal" are synonyms. (2) a particular stored sequence of moving images, e.g., on a tape or within a database. video amplifier (1) in television, the wideband stage (or stages) that amplifies the picture signal and presents it to the picture tube. (2) A similar wideband amplifier, such as an instrument amplifier or preamplifier having at least a 4-MHz bandwidth. video coding compression of moving images. Coding can be done purely on an Intraframe (within-frame) basis, using a still image-coding algorithm, or by exploiting temporal correlations between frames (interframe coding). In the latter case, the encoder estimates motion between the current frame and a previously-coded reference frame, encodes a field of motion vectors that describe the motion compactly, generates a motion-compensated prediction image and codes the difference between this and the actual frame with an intraframe residue coder--typically the 8 × 8 discrete cosine transform. The decoder receives the motion vectors and encoded residue, constructs the prediction picture from its stored reference frame and adds back the difference information to recover the frame. See MPEG. video compression See video coding. a pallet of 262144, or 320×240 with 256 colors selected from a pallet of 262144. video RFI undesired radio-frequency signals that compete with the desired video signal. video signal the video signal in the U.S. is defined by the NTSC standard. See National Television System Committee. video signal processing The area of specialization concerned with the processing of time sequences of image data, i.e., video. video transmission the combined amplitudemodulated carrier, sync, and blanking pulses that make up a video signal. virtual address (1) an address that refers to a location of virtual memory. (2) the address generated by the processor in a paging (virtual memory) system. Compare with real address. virtual channel a concept used to describe unidirectional transport of ATM cells associated by a common unique identifier value. virtual circuit an abstraction that enables a fraction of a physical circuit to be allocated to a user. To a user, a virtual circuit appears as a physical circuit; multiple virtual circuits can be multiplexed onto a single physical circuit. virtual connection a representation of the circuit between the input leads of an ideal op-amp. The voltage across and the current through a virtual connection are both zero. If one input lead of an ideal op-amp is connected to ground, the virtual connection is often termed a virtual ground. virtual DMA DMA in which virtual addresses are translated into real addresses during the I/O operation. virtual instrument an instrument created through computer control of a collection of
A 24 GHz frequency synthesizer for automotive collision avoidance radar
Published in International Journal of Electronics Letters, 2020
The proposed VCO is shown in Figure 6. The VCO is designed with modified current-reuse scheme. The current-reuse scheme is modified with the implementation of NMOS capacitive source degenerated cross-coupled transistors cascoded with the N/PMOS transistors of current-reuse scheme. This modified current-reuse scheme enhances the negative resistance for LC tank circuit and increases the transconductance of the VCO. To decrease the phase noise and power consumption in the designed VCO, the N/PMOS cross-coupled transistors are biased in subthreshold region. These transistors operate in a differential mode and provide a virtual ground. This virtual ground node X is connected with capacitively source degenerated terminal of cascoded NMOS cross-coupled transistors. This configuration is highly favourable because the loss of on-chip inductors over a wide frequency band can be compensated. Since Cs blocks the dc current, it is necessary to parallel a resistor to this capacitor to provide the dc path required for biasing the NMOS transistors. The value of the biasing resistor must be several times larger than the impedance of Cs and small enough to provide the dc current needed for producing the required gm for compensating the loss of LC tank at those frequencies in which the negative circuits effectively compensate for the loss of on-chip inductors.