Topic
Output impedance
About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.
Papers published on a yearly basis
Papers
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TL;DR: Good linearity performance (ACPR and EVM) demonstrates the applicability of inverter-based class-D amplifiers for outphasing configurations.
Abstract: A 2.4 GHz outphasing power amplifier (PA) is implemented in a 32 nm CMOS process. An inverter-based class-D PA topology is utilized to obtain low output impedance and good linearity in the outphasing system. MOS switch non-idealities, such as finite on-resistance and finite rise and fall times are analyzed for their impact on outphasing linearity and efficiency. Outphasing combining is performed via a transformer configured to achieve reduced loss at power backoff. The fabricated class-D outphasing PA delivers 25.3 dBm peak CW power with 35% total system Power Added Efficiency (includes all drivers). Average OFDM power is 19.6 dBm with efficiency 21.8% when transmitting WiFi signals with no linearization required. The PA is packaged in a flip-chip BGA package. Good linearity performance (ACPR and EVM) demonstrates the applicability of inverter-based class-D amplifiers for outphasing configurations.
100 citations
TL;DR: In this paper, the authors proposed to increase the linearity of the low-noise amplifier (LNA) or decrease its power consumption, which is required for multimode designs, with little degradation in NF.
Abstract: The optimum collector current density, at the global minimum noise figure (NF) point for a bipolar transistor, scales linearly with frequency. The optimum source impedance, on the other hand, remains constant if the device area is scaled inversely with frequency. As a result, transforming the design from one frequency to another can be achieved by simple circuit scaling. Taking advantage of the shallow nature of the NF/sub min/ global minima, it is possible to increase the linearity of the low-noise amplifier (LNA) or decrease its power consumption, which is required for multimode designs, with little degradation in NF. These theoretical results have been applied to LNA and active mixer designs, and verified by constructing a 1.8-GHz frequency-scaled SiGe bipolar test chip. The measured LNA NF is 1.3 dB at 4.5 mA, while the double-balanced mixer achieves a single-sideband (SSB) NF of 6.1 dB for the low-linearity mode and an IIP3 and an SSB NF of +3 dBm and 6.6 dB, respectively, for the high-linearity mode.
99 citations
07 Aug 2002
TL;DR: In this article, the transient response of voltage regulator modules (VRMs) based on small-signal models is discussed, and a constant resistive output impedance design for the VRM is proposed, and its limitation in application is analyzed.
Abstract: This paper discusses the transient response of voltage regulator modules (VRMs) based on small-signal models. The concept of constant resistive output impedance design for the VRM is proposed, and its limitation in application is analyzed. The impact of the output filter and the feedback control bandwidth shows that there is an optimum design for the VRM to achieve fast transient response, small size and good efficiency. Simulations and experimental results prove the theoretical analysis.
99 citations
TL;DR: A current source suitable for Electrical Impedance Tomography (EIT) was simulated using a SPICE model, and built to verify stable operation, which provides 80 dB precision for this EIT application.
Abstract: The Howland current pump is a popular bioelectrical circuit, useful for delivering precise electrical currents. In applications requiring high precision delivery of alternating current to biological loads, the output impedance of the Howland is a critical figure of merit that limits the precision of the delivered current when the load changes. We explain the minimum operational amplifier requirements to meet a target precision over a wide bandwidth. We also discuss effective compensation strategies for achieving stability without sacrificing high frequency output impedance. A current source suitable for Electrical Impedance Tomography (EIT) was simulated using a SPICE model, and built to verify stable operation. This current source design had stable output impedance of 3.3 MΩ up to 200 kHz, which provides 80 dB precision for our EIT application. We conclude by noting the difficulty in measuring the output impedance, and advise verifying the plausibility of measurements against theoretical limitations.
99 citations
01 Jul 1999
TL;DR: In this article, a DC distributed power system, the interaction between individually designed power modules/subsystems may cause the instability of the whole system in the small-signal sense, these kinds of interactions can be predicted by checking impedance ratio Z/sub o/Z/sub i and can also be prevented by making impedance specification for power module/subs.
Abstract: In a DC distributed power system, the interaction between individually designed power modules/subsystems may cause the instability of the whole system In the small-signal sense, these kinds of interactions can be predicted by checking impedance ratio Z/sub o//Z/sub i/ and can also be prevented by making impedance specification for power modules/subsystems Many efforts have been made in defining impedance specification and improving I/O impedance for converters and filters This paper summarizes work in these two areas
99 citations