GB1027249A - Improvements in voltage clamps - Google Patents

Improvements in voltage clamps

Info

Publication number
GB1027249A
GB1027249A GB3968463A GB3968463A GB1027249A GB 1027249 A GB1027249 A GB 1027249A GB 3968463 A GB3968463 A GB 3968463A GB 3968463 A GB3968463 A GB 3968463A GB 1027249 A GB1027249 A GB 1027249A
Authority
GB
United Kingdom
Prior art keywords
amplifier
base
capacitor
input
transistor
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.)
Expired
Application number
GB3968463A
Inventor
John Victor James Corney
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.)
THORN ELECTRONICS Ltd
Original Assignee
THORN ELECTRONICS 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 THORN ELECTRONICS Ltd filed Critical THORN ELECTRONICS Ltd
Priority to GB3968463A priority Critical patent/GB1027249A/en
Publication of GB1027249A publication Critical patent/GB1027249A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00Details of television systems
    • H04N5/14Picture signal circuitry for video frequency region
    • H04N5/16Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level
    • H04N5/18Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level by means of "clamp" circuit operated by switching circuit
    • H04N5/185Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level by means of "clamp" circuit operated by switching circuit for the black level

Abstract

1,027,249. Transistor circuits; television. THORN ELECTRONICS Ltd. Oct. 8, 1963, No. 39684/63. Headings H3T and H4F. The output voltage of a D.C. amplifier having a series input capacitor is periodically clamped by rendering periodically active a negative feedback path which charges or discharges the capacitor through a constant current device at a rate dependent upon the difference between the amplifier output voltage and a reference voltage. Television signals are applied through input capacitor C1 to an amplifier comprising transistors VT6-VT9 and having negative feedback between the emitter of the output transistor VT9 and the base of VT8. During the back porch period an input pulse at the base of VT5 causes VT1, the common emitter load of comparator transistors VT2, VT3, to become conductive so that the output voltage of the amplifier is compared with the reference voltage applied to the base of VT2. The latter transistor is coupled to the base of a transistor VT4 forming with VT3 a constant current charge and discharge path for the capacitor which resets the D.C. input level and thus the output level. During the restoration period the amplifier is thus provided with a negative feedback path which effectively reduces the input impedance of the amplifier to a low value so that the capacitor voltage will be quickly reset. Diode MR prevents VT3 passing current when the restoration circuit is not in use and diode MR2 prevents forward conduction between collector and base of VT7 if the base is driven negative. Large positive input signals will cause VT6 to cut off and VT7 to bottom so that the signals will be amplitude limited.
GB3968463A 1963-10-08 1963-10-08 Improvements in voltage clamps Expired GB1027249A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB3968463A GB1027249A (en) 1963-10-08 1963-10-08 Improvements in voltage clamps

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3968463A GB1027249A (en) 1963-10-08 1963-10-08 Improvements in voltage clamps

Publications (1)

Publication Number Publication Date
GB1027249A true GB1027249A (en) 1966-04-27

Family

ID=10410906

Family Applications (1)

Application Number Title Priority Date Filing Date
GB3968463A Expired GB1027249A (en) 1963-10-08 1963-10-08 Improvements in voltage clamps

Country Status (1)

Country Link
GB (1) GB1027249A (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2035161A1 (en) * 1969-03-21 1970-12-18 Rca Corp
JPS4852130A (en) * 1971-10-29 1973-07-21
JPS5136619U (en) * 1974-09-10 1976-03-18
JPS5152762A (en) * 1974-09-09 1976-05-10 Rca Corp
FR2390064A1 (en) * 1977-05-05 1978-12-01 Rca Corp
FR2399169A1 (en) * 1977-07-28 1979-02-23 Rca Corp latch circuit combines the blanking level and polarization of the picture tube for a television signal processing system
FR2420888A1 (en) * 1978-03-22 1979-10-19 Rca Corp Circuit automatic adjustment of brightness using a closed loop adjustment stabilized vis-a-vis an interruption by large amplitude video signals

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2035161A1 (en) * 1969-03-21 1970-12-18 Rca Corp
JPS4852130A (en) * 1971-10-29 1973-07-21
JPS5233932B2 (en) * 1971-10-29 1977-08-31
JPS5152762A (en) * 1974-09-09 1976-05-10 Rca Corp
JPS581869B2 (en) * 1974-09-09 1983-01-13 Rca Corp
JPS5136619U (en) * 1974-09-10 1976-03-18
JPS5515421Y2 (en) * 1974-09-10 1980-04-09
FR2390064A1 (en) * 1977-05-05 1978-12-01 Rca Corp
FR2399169A1 (en) * 1977-07-28 1979-02-23 Rca Corp latch circuit combines the blanking level and polarization of the picture tube for a television signal processing system
FR2420888A1 (en) * 1978-03-22 1979-10-19 Rca Corp Circuit automatic adjustment of brightness using a closed loop adjustment stabilized vis-a-vis an interruption by large amplitude video signals

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