GB1228412A - - Google Patents
Info
- Publication number
- GB1228412A GB1228412A GB1228412DA GB1228412A GB 1228412 A GB1228412 A GB 1228412A GB 1228412D A GB1228412D A GB 1228412DA GB 1228412 A GB1228412 A GB 1228412A
- Authority
- GB
- United Kingdom
- Prior art keywords
- drain
- transistor
- path
- shunt
- source
- 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
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/222—Studio circuitry; Studio devices; Studio equipment
- H04N5/262—Studio circuits, e.g. for mixing, switching-over, change of character of image, other special effects ; Cameras specially adapted for the electronic generation of special effects
- H04N5/265—Mixing
-
- 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 FET type devices
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Control Of Amplification And Gain Control (AREA)
Abstract
1,228,412. Gain control; transistor switching circuit. BRITISH BROADCASTING CORP. 12 March, 1969 [5 March, 1968], No. 10706/68. Headings H3T and H4N. A fader X, Fig. 1, comprises a series resistor 21 connected to an input terminal 11 and feeding the drain-source path of a F.E.T. 10, connected to an output terminal 12, with the collector emitter path of a junction transistor 30 connected in shunt across the signal path between the drain of the FET and signal earth. Control voltage is applied to the gate of the F.E.T. and the base of the junction transistor to differentially vary their impedances. The arrangement reduces the effect of the source drain capacitance at high attenuation settings of the fader, preventing cross-talk. The junction transistor 30 may be provided with negative feed-back from emitter to collector by a further transistor (31) Fig. 2 (not shown), to provide a lower impedance shunt path. In addition the potential controlling the impedance of the shunt transistor 30 may be derived from the drain source voltage of the F.E.T., e.g. from the drain, since the terminal 14 is connected to a virtual earth at the low impedance input of amplifier 17.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1070668 | 1968-03-05 |
Publications (1)
Publication Number | Publication Date |
---|---|
GB1228412A true GB1228412A (en) | 1971-04-15 |
Family
ID=9972782
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB1228412D Expired GB1228412A (en) | 1968-03-05 | 1968-03-05 |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB1228412A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2373916A1 (en) * | 1976-12-07 | 1978-07-07 | Tekade Felten & Guilleaume | CONTROLABLE ELECTRONIC RESISTANCE |
FR2596602A1 (en) * | 1986-03-28 | 1987-10-02 | Telediffusion Fse | VIDEO SIGNAL MIXER DEVICE |
-
1968
- 1968-03-05 GB GB1228412D patent/GB1228412A/en not_active Expired
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2373916A1 (en) * | 1976-12-07 | 1978-07-07 | Tekade Felten & Guilleaume | CONTROLABLE ELECTRONIC RESISTANCE |
FR2596602A1 (en) * | 1986-03-28 | 1987-10-02 | Telediffusion Fse | VIDEO SIGNAL MIXER DEVICE |
EP0240417A1 (en) * | 1986-03-28 | 1987-10-07 | Etablissement Public Télédiffusion de France | Device for mixing video signals |
US4845565A (en) * | 1986-03-28 | 1989-07-04 | Telediffusion De France | Video signal mixer device |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PS | Patent sealed | ||
PLNP | Patent lapsed through nonpayment of renewal fees |