Output impedance

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

The NBS conical transducer: Analysis

Abstract: The NBS conical transducer is a sensitive, broadband device for the measurement of surface displacement as a function of time. Its uses include acoustic‐emission testing. Here, the operation of this transducer is subjected to a straightforward analysis. Although several approximations, some more dubious than others, are made, the model predicts the main features rather well. The important parameters are the size and shape of the active element, the source impedance (looking into the area whose deflection is being measured), and the terminating impedance (back load).

A wearable ear-EEG recording system based on dry-contact active electrodes

Abstract: This work reports an ear-EEG acquisition system with dry-contact active electrodes for future wearable applications. Employing dedicated chopper buffer in the active electrodes, a prototype fabricated in a 0.18-µm CMOS demonstrates input impedance as large as 18GΩ@DC and 6.7GΩ@50Hz, and 3.03fA/vHz input current noise, and a total input-referred noise (IRN) of 0.67µV rms in 0.5–100Hz bandwidth. System's CMRR in combination with active electrodes is higher than 100dB@DC. Under large source impedance imbalance of 1MΩ, a 78-dB@50Hz CMRR is still obtained. To validate the system's ability to record EEG, an auditory stead-state response was measured, showing same SNR with wet electrodes and a commercial EEG amplifier.

Design of Parallel Resonant Switched-Capacitor Equalizer for Series-Connected Battery Strings

Abstract: The traditional pure switched-capacitor equalizer suffers from a large inrush current and low balance speed. An automatic parallel resonant switched-capacitor equalizer (PReSCE) for series-connected battery strings is proposed, which utilizes resonant switched-capacitor to eliminate the inrush current. The parallel ReSC converters not only minimizes output impedance at the low switching frequency, but delivers the excess energy to the low-voltage battery directly from the high-voltage battery in one cycle. Both of the two functions increase the balance speed. All of the switches are controlled by a pair of complementary pulsewidth modulation signals at a fixed operational frequency. Both simulation and experiment are used to verify the theoretical analysis and system feasibility of the proposed circuit. The results show that the PReSCE circuit eliminates the inrush current and increases the balance speed three times than the parallel pure switched-capacitor equalizer.

Control and implementation of a three-phase voltage-doubler reversible AC to DC converter

Abstract: In this paper, a novel three-phase bidirectional interface is proposed by using only four active switches to simplify the hardware circuit and achieve unity power factor, sinusoidal input current, adjustable output voltage and bidirectional power flow capability. To ensure obtaining clean input current waveform, the current tracking mechanism is analyzed together with graphical aid and some critical design conditions are presented. Finally, a small-signal model is derived and, in addition to the feedback control, an instantaneous voltage detector is proposed for the added feedforward control to achieve almost zero output impedance and zero audio susceptibility. A prototype hardware circuit is constructed and some experimental results are presented for demonstration. >

Line driver with adaptive output impedance

Abstract: A line driver comprising: an input terminal (2) for receiving an input signal, an output terminal (10) for connecting a load (8), a first (12) and a second (22) transconductance-controlled transconductor having substantially equal transconductances, each transconductor having a non-inverting input (14; 24), an inverting input (16; 26), an output (18; 28) and a common control input (20) for controlling the transconductance, the non-inverting inputs (14; 24) of the first (12) and second (22) transconductors being coupled to the input terminal (2), the outputs (18; 28) of the first (12) and second (22) transconductors being coupled to the output terminal (10), the inverting input (16) of the first transconductor (12) being coupled to a point (6) of reference potential, the inverting input (26) of the second transconductor (22) being coupled to the output terminal (10), and an amplifier (32) having a non-inverting input (34), an inverting input (36) and an output (38) coupled to, respectively, the input terminal (2), the output terminal (10) and the common control input (20) of the first (12) and the second (22) transconductors.