Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

Interconnect coupling noise in CMOS VLSI circuits

Abstract: AbstmctInterconnect between a CMOS driver and receiver can be modeled as a lossy transmission line in high speed CMOS VLSI circuits as transition times become comparable to or lass than the time of flight delay of the signal through the low resistivity interconnect. In this paper, closed form expressions for the coupling noise between adjacent interconnect are presented to estimate the coupling noise voltage on a quiet line. These expressions are based on an assumption that the interconnections are loosely coupled, where the effect of the coupling noise on the waveform of the active line is small and can be neglected. It is demonstrated that the output impedance of the CMOS driver should preferably be comparable to the interconnect impedance in order to reduce the propagation delay of the CMOS driver stage.

Extraction of Common-Mode Impedance of an Inverter-Fed Induction Motor

Abstract: In a variable speed drive (VSD) system, high-frequency switching of power devices will cause large common-mode (CM) voltage during operation. While the CM voltage acts on the parasitic capacitance of the system, it will generate serious CM current on the motor side. It is necessary to model the VSD system so as to analyze and forecast the CM current theoretically. However, an essential condition of modeling CM current is to extract the CM impedance on the motor side of the system. In this paper, a novel extraction method for the CM impedance of an inverter-fed induction motor is proposed. First of all, time-domain waveforms of the CM voltage and current on the motor side of the VSD system are measured, and then mathematical calculations are performed to obtain the spectrum characteristics of the CM impedance on the motor side of the system. Compared to the traditional extraction methods of the impedance parameter by an impedance measurement or numerical calculation, the method proposed in this paper does not require laborious modeling of the motor or cable, and the extraction process is much simpler and easier. Moreover, in traditional methods, the motor impedance parameters are usually obtained in a nonworking state, while the proposed extraction method can be conducted in working state. Thus, the CM impedance extracted by the proposed method will be more accurate. Through comparing measurement and the simulation results of the CM current on motor side, the proposed CM impedance extraction method for an inverter-fed induction motor is validated.

Multiloop feedback control apparatus for DC/DC converters with frequency-shaping band pass current control

Abstract: A switched mode power converter includes a periodically switched power switch which is switched under the control of a multiple loop feedback controlling the power switch in order to supply a regulated output. The output voltage and power switch current are sensed. An error voltage is generated which is representative of the deviation of the output voltage from a regulated value. A voltage derived from the power switch current is limited in its low frequency response and is then combined with the error voltage. The low frequency response of the current loop gain is used to maintain an advantageously low output impedance for the power supply. This shaped loop gain response advantageously allows accurate adjustment of the current loop gain and reduces the system to a lower order while maintaining adequate loop stability. The low frequency response may be attained by limiting the low frequency response of the sensed current or by inserting an operational amplifier in the feedback path to limit its low frequency response.

Methods and apparatus for measuring impedance in the body

Abstract: Methods and apparatus are provided for measuring the impedance of a patient's body. Pulse generating circuitry within a rate-responsive pacemaker is used to generate an impedance measurement signal that is applied to the body of the patient with conventional pacemaker leads. The impedance measurement signal contains a series of multiphasic impedance measurement waveforms, which have no net DC value and zero value after second integration. The impedance measurement signal allows the impedance of the body to be measured without interfering with external cardiac monitoring equipment such as electrocardiogram machines.

Microstrip impedance matching circuit with harmonic terminations

Abstract: A microstrip impedance matching circuit has fixed harmonic terminations in the form of a pair of open-circuited stubs, each having a length equal to a quarter wavelength of a different harmonic frequency, connected to the main transmission line to cause the impedance at the harmonic frequencies to be made constant irrespective of the nature of the load impedance at the harmonic frequencies.