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NL7415210A - Filter with automatically controlled variable cut off frequency - has output level maintained constant via amplifier with resistive feedback and FET. - Google Patents

Filter with automatically controlled variable cut off frequency - has output level maintained constant via amplifier with resistive feedback and FET.

Info

Publication number
NL7415210A
NL7415210A NL7415210A NL7415210A NL7415210A NL 7415210 A NL7415210 A NL 7415210A NL 7415210 A NL7415210 A NL 7415210A NL 7415210 A NL7415210 A NL 7415210A NL 7415210 A NL7415210 A NL 7415210A
Authority
NL
Netherlands
Prior art keywords
filter
frequency
automatically controlled
amplifier
fet
Prior art date
Application number
NL7415210A
Other languages
Dutch (nl)
Original Assignee
Takeda Riken Ind Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Takeda Riken Ind Co Ltd filed Critical Takeda Riken Ind Co Ltd
Priority to NL7415210A priority Critical patent/NL7415210A/en
Publication of NL7415210A publication Critical patent/NL7415210A/en

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H11/00—Networks using active elements
    • H03H11/02—Multiple-port networks
    • H03H11/04—Frequency selective two-port networks
    • H03H11/12—Frequency selective two-port networks using amplifiers with feedback
    • H03H11/1291—Current or voltage controlled filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
    • H03G1/007—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements using field-effect transistors [FET]
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G5/00—Tone control or bandwidth control in amplifiers
    • H03G5/16—Automatic control
    • H03G5/18—Automatic control in untuned amplifiers
    • H03G5/22—Automatic control in untuned amplifiers having semiconductor devices

Landscapes

  • Networks Using Active Elements (AREA)

Abstract

Filter with an automatically controlled variable cut-off frequency. The cut-off frequency is automatically changed as a function of an input signal frequency, and where the output signal is maintained at a constant fixed level. The filter is designed as a voltage controlled low pass RC filter. An amplifier (2) has its input connected to the non-inverted input terminal (5) via two resistors (3, 4). The non-inverted input of the amplifier is connected to earth, the amplifier has resistive feed-back (6, 7) which is connected to the inverted input via a variable element formed by a field effect transistor (8). A detector is used to measure the level of the output and provides a control signal to the variable element which controls the filter circuit.
NL7415210A 1974-11-21 1974-11-21 Filter with automatically controlled variable cut off frequency - has output level maintained constant via amplifier with resistive feedback and FET. NL7415210A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
NL7415210A NL7415210A (en) 1974-11-21 1974-11-21 Filter with automatically controlled variable cut off frequency - has output level maintained constant via amplifier with resistive feedback and FET.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7415210A NL7415210A (en) 1974-11-21 1974-11-21 Filter with automatically controlled variable cut off frequency - has output level maintained constant via amplifier with resistive feedback and FET.

Publications (1)

Publication Number Publication Date
NL7415210A true NL7415210A (en) 1976-05-25

Family

ID=19822517

Family Applications (1)

Application Number Title Priority Date Filing Date
NL7415210A NL7415210A (en) 1974-11-21 1974-11-21 Filter with automatically controlled variable cut off frequency - has output level maintained constant via amplifier with resistive feedback and FET.

Country Status (1)

Country Link
NL (1) NL7415210A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0158231A3 (en) * 1984-04-11 1988-01-27 Hitachi, Ltd. Filter integrated circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0158231A3 (en) * 1984-04-11 1988-01-27 Hitachi, Ltd. Filter integrated circuit

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Legal Events

Date Code Title Description
BV The patent application has lapsed