JPS55109011A - Automatic gain control circuit - Google Patents

Automatic gain control circuit

Info

Publication number
JPS55109011A
JPS55109011A JP1545379A JP1545379A JPS55109011A JP S55109011 A JPS55109011 A JP S55109011A JP 1545379 A JP1545379 A JP 1545379A JP 1545379 A JP1545379 A JP 1545379A JP S55109011 A JPS55109011 A JP S55109011A
Authority
JP
Japan
Prior art keywords
turned
agc
time constant
circuit
noise
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
JP1545379A
Other languages
Japanese (ja)
Inventor
Hiroto Yasumura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Corp
Original Assignee
Toshiba Corp
Tokyo Shibaura Electric 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 Toshiba Corp, Tokyo Shibaura Electric Co Ltd filed Critical Toshiba Corp
Priority to JP1545379A priority Critical patent/JPS55109011A/en
Priority to US06/042,345 priority patent/US4292598A/en
Priority to DE2921777A priority patent/DE2921777C2/en
Priority to GB7918917A priority patent/GB2026269B/en
Publication of JPS55109011A publication Critical patent/JPS55109011A/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H03G3/345—Muting during a short period of time when noise pulses are detected, i.e. blanking

Abstract

PURPOSE:To avoid occurrence of the excessive output by cutting off the AGC loop to the pulse-type noise to secure increment of the AGC time constant and then decreasing contrarily the AGC time constant apparently to the arrival of the excessive signal to secure the immediate countermeasure to the excessive signal respectively. CONSTITUTION:When the pulse-type noise mixes into the signal and the noise level is at the fixed value, transistors TrQ4 and Q2 are turned on with TrQ5 and Q3 are turned on with TrQ5 and Q3 turned off respectively. With TrQ5 turned off, and accordingly TrQ6 is turned off. Thus the route is cut off between AGC detection amplifier 29 and AGC time constant circuit 32, and then the AGC loop is cut off. On the other hand, noise detection circuit 30 detects the noise and then turns TrQ7 on. And TrQ10 is on since excessive signal detection circuit 31 has no operation. As a result, TrQ11 is turned on with the time constant increased for circuit 32. When the excessive signal arrives, Q9 of circuit 31 is turned on. Then the charge of capacitor 43 is discharged via TrQ4 and Q9.
JP1545379A 1978-06-01 1979-02-15 Automatic gain control circuit Pending JPS55109011A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
JP1545379A JPS55109011A (en) 1979-02-15 1979-02-15 Automatic gain control circuit
US06/042,345 US4292598A (en) 1978-06-01 1979-05-25 Automatic gain control circuit
DE2921777A DE2921777C2 (en) 1978-06-01 1979-05-29 Automatic gain control circuit
GB7918917A GB2026269B (en) 1978-06-01 1979-05-31 Automatic gain control circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1545379A JPS55109011A (en) 1979-02-15 1979-02-15 Automatic gain control circuit

Publications (1)

Publication Number Publication Date
JPS55109011A true JPS55109011A (en) 1980-08-21

Family

ID=11889212

Family Applications (1)

Application Number Title Priority Date Filing Date
JP1545379A Pending JPS55109011A (en) 1978-06-01 1979-02-15 Automatic gain control circuit

Country Status (1)

Country Link
JP (1) JPS55109011A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6257308A (en) * 1985-09-06 1987-03-13 Iwatsu Electric Co Ltd Automatic gain control circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6257308A (en) * 1985-09-06 1987-03-13 Iwatsu Electric Co Ltd Automatic gain control circuit

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