NDLI: Low-frequency reactance amplifier

Content Provider	IEEE Xplore Digital Library
Author	Biard, J.R.
Copyright Year	1963
Abstract	A reactance amplifier has been constructed which is capable of low-noise amplification at audio and subaudio frequencies [1]. Stable voltage amplification of 20-30 db and noise figures as low as 0.16 db (50-K source resistance) have been observed for signal frequencies between 2 and 50 cps. The circuit configuration is a double sideband up-converter or modulator in which a band of frequencies from dc to several hundred cycles is used to modulate a 150-kc carrier. An analysis for noise and gain is presented which considers the average, fundamental, and second-harmonic components of the time-varying diode capacitance. The amplifier input is a signal at low audio frequency, while the output is composed of the sum and difference sidebands of the pump. Gain is realized through up-converter action associated with the frequency shift from signal frequency to near pump frequency; the sum and difference sidebands are further amplified in the output tank by the negative resistance resulting from the action of the component of time-varying capacitance at the second harmonic of the pump frequency. Gain and equivalent input noise resistance are discussed as functions of detuning in the passive output tank; measured and calculated results are compared. A scheme is also presented for stabilizing the amplifier at high values of negative resistance gain.
Sponsorship	IEEE Publication
Starting Page	298
Ending Page	303
Page Count	6
File Size	509096
File Format	PDF
ISSN	00189219
Volume Number	51
Issue Number	2
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	1963-02-01
Publisher Place	U.S.A.
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Frequency Capacitance Low-noise amplifiers Voltage Noise figure Circuit noise Diodes Electrical resistance measurement Gain measurement Noise measurement
Content Type	Text
Resource Type	Article
Subject	Computer Science Electrical and Electronic Engineering

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