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FET amplifier
About: FET amplifier is a research topic. Over the lifetime, 7048 publications have been published within this topic receiving 77549 citations.
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05 Aug 1994TL;DR: In this paper, an amplifier capable of being tuned to provide linear gain over a selected input signal range is described, where the output and input stages are arranged in a folded-cascode configuration so as to improve the output impedance and input common-mode signal range of the amplifier.
Abstract: An amplifier capable of being tuned to provide linear gain over a selected input signal range is disclosed herein. The amplifier includes an input stage for receiving an input signal. The amplifier further includes a tuning circuit, connected between the input stage and an amplifier output stage, for controlling gain of the amplifier by adjusting a tuning current supplied to the amplifier output stage. The tuning circuit may be realized with a differential transistor pair connected to a pair of transistors within the output stage. In a preferred implementation the input and output stages are arranged in a folded-cascode configuration so as to improve the output impedance and input common-mode signal range of the amplifier.
27 citations
TL;DR: In this article, a pseudomorphic GaAs/InGaAs high electron mobility transistor was used for a cryogenic amplifier for ∼100 kHz to a few MHz, which uses a commercially available pseudomorphic GAAs/INGaAs HEM transistor and dissipates less than 0.5 mW in the cryogenic stage.
Abstract: A cryogenic amplifier for ∼100 kHz to a few MHz is presented which uses a commercially available pseudomorphic GaAs/InGaAs high electron mobility transistor and dissipates less than 0.5 mW in the cryogenic stage. The input-referred voltage noise and current noise of the amplifier at approximately 2 MHz are measured to be approximately 0.7 nV Hz−1/2 and 25 fA Hz−1/2, respectively. A superconducting resonant circuit can be used to provide a high input impedance over a narrow bandwidth, or a low input impedance can be used to yield a large bandwidth. Although suitable for many applications, the amplifier has been developed for measurements of current noise from a high-impedance source, and its long-term stability is such that by averaging over 30 min, it could be used to detect approximately 0.6 fA Hz−1/2.
27 citations
TL;DR: In this paper, it was shown that the outgoing noise waves at the input and output of a balanced amplifier are uncorrelated even though they originate in the same components, and that a sliding short-circuit at the output produces no variation in the output noise of the amplifier.
Abstract: The balanced amplifier is used in applications requiring a better input match than is possible with a single-ended amplifier. While the impedance matching property of the balanced amplifier is well known, its noise behavior appears not to be widely understood. It is shown that the outgoing noise waves at the input and output of a balanced amplifier are uncorrelated even though they originate in the same components. Hence, a sliding short-circuit at the input produces no variation in the output noise of the amplifier. The properties of a balanced amplifier are similar to those of an amplifier preceded by an isolator, although the noise wave emerging from inputs of the two circuits originates in different elements. The noise theory of the balanced amplifier applies also to balanced mixers based on quadrature hybrids.
27 citations
01 Apr 1989
TL;DR: In this paper, a bootstrap transimpedance amplifier was proposed to combine the effective stability of negative feedback with the desirable features of the positive type of feedback for photodetector applications.
Abstract: In any photodetector application, capacitance is a major factor which limits response time. Decreasing load resistance improves this aspect, but at the expense of sensitivity. In the subsequent amplifier, positive feedback may be used with caution. It is possible to combine the effective stability of negative feedback with the desirable features of the positive type. An alternative approach, the bootstrap transimpedance amplifier, has been investigated. This offers the usual advantages of the transimpedance amplifier together with an effective capacitance reduction technique.
27 citations
TL;DR: A two-electrode biopotential amplifier, designed for low-supply voltage (2.7–5.5 V), is presented, which has high differential and sufficiently low common mode input impedances achieved by means of positive feedback, implemented with an original interface stage.
Abstract: Portable biomedical instrumentation has become an important part of diagnostic and treatment instrumentation. Low-voltage and low-power tendencies prevail. A two-electrode biopotential amplifier, designed for low-supply voltage (2.7–5.5 V), is presented. This biomedical amplifier design has high differential and sufficiently low common mode input impedances achieved by means of positive feedback, implemented with an original interface stage. The presented circuit makes use of passive components of popular values and tolerances. The amplifier is intended for use in various two-electrode applications, such as Holter monitors, external defibrillators, ECG monitors and other heart beat sensing biomedical devices.
27 citations