Title: Variable-gain amplifier

Abstract: A variable-gain amplifier comprises a transistor with an emitter connected in a degenerative emitter-follower circuit which includes a PIN diode traversed by a current injector in the form of an operational amplifier, the PIN diode forming part of a negative-feedback path extending from the output to the inverting input of the operational amplifier. To achieve a gain characteristic whose logarithm varies linearly with a control voltage, this control voltage is fed to the same inverting input through an amplifier circuit with an exponential characteristic, including another operational amplifier provided with an input transistor. A temperature-compensating circuit, preceding that input transistor, comprises still another operational amplifier having a further transistor inserted in its negative-feedback path. The variable-gain amplifier may be included in one of two conjugate (sum and difference) channels of a monopulse radar.

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Inventors: Berrod, Francois (Paris, FR)
Puverel, Fernand (Paris, FR)

Application Number: 407996
Filing Date: 1973-10-19
Publication_date: 1976-03-02
Assignee: Thomson-CSF (Paris, FR)
Primary Class(es): 342/92 330/86, 330/145, 330/283, 330/284, 330/289, 342/149, 342/205
Other Classes:
US Patent Ref:

3550028	Dec, 1970	Dille, Jr. et al.	330/145.
3582807	Jun, 1971	Addis	330/29.
3624561	Nov, 1971	Tongue	330/145.
3708699	Jan, 1973	Frei et al.	330/29.
3708754	Jan, 1973	Diehl	330/28.
3710270	Jan, 1973	Addis et al.	330/29.
3723894	Mar, 1973	Benenati	330/29.
3743770	Jul, 1973	Vidovic	330/29.
3774118	Nov, 1973	Doorn	330/28.

Other Refs:
Primary Examiner: Tubbesing, T. H.
Assistant Examiner: Montone, G. E.
Attorney: Ross; Karl F., Dubno; Herbert