Video circuits

Index

• Video transmitters
• Video modulators
• Video distribution
• Video switching
• Digital video technology
• Equipment modifications
• Video conversion
• Video mixers and effects
• Video overlay
• Video signal generating circuits

General video circuit topics

• AGC disciplines RF and fiber signals so they "ain't misbehavin'" - you may need AGC to keep wayward RF, optical, and video signals within acceptable bounds

Video distribution

Basic video amplifier circuits

• Fast, Stable Wideband FET Amplifier - a gain-trimmable wideband FET amplifier with very good speed, high input impedance, and excellent dc stability under all conditions, more than adequate performance for driving video cable, high-speed data converters, etc.
• New Amplifiers Simplify Wideband Techniques - article describes some video amplifier ICs from Maxim and applications for them like coaxial cable driving and twisted pair cable video transmission
• Positive Feedback Terminates Cables - positive feedback along with a series output resistor can provide a controlled output impedance from an op-amp circuit, with lower losses than would result from using an actual resistor
• Video amplifier circuit from discrete transistors
• Video Circuits Collection - many video amplifier circuits in pdf format, includes video transmission over UTP

Video signal splitting to multiple monitors

• Driving Multiple VGA Monitors - simple multiple-monitor driver circuit
• The Audio / Video Distribution Amplifier - has 3 outputs from one input
• Video signal amplifier - take the video signals from your VCR and will amplify them sufficiently to drive up to 3 monitors

Coaxial cable video transmission

• Camera power and video use same coax cable - it is convenient to run both the power and the video signal through one coax cable but it needs some extra electronics on both ends of the coaxial cable
• New Amplifiers Simplify Wideband Techniques - example drixing circuit for coaxial cables and twisted pair video transmission

Video signal isolation

Video signal galvanic isolation is sometimes needed to avoid problems related to ground loops in video systems.

• HCPL-4562 and HCNW4562 optocouplers - datasheet includes video isolator circuit diagrams

Differenatial video signals

Methods for transmitting video signals over unshielded twisted pair wiring.

• Circuit adapts differential input to drive coax - uses an HFA1100 or HFA1105 to convert a balanced input signal to a single-ended output signal, uses positive feedback to characteristic-impedance matching while increasing the available output swing, as compared with using a simple series termination resistor
• Color video travels on twisted-pair cable - telephone lines and local-area networks commonly use inexpensive twisted-pair cables, video-system designers can also take advantage of this low-cost cable to transmit composite-color-video signals using this circuit
• Color video travels on twisted-pair cable - circuit based on few LM6181 amplifiers
• IC forms differential line driver/receiver - you can use the HFA1212 dual video buffer to implement differential line drivers and receivers with a minimum of external components
• Instrumentation amplifier has 290-MHz gain-bandwidth product - very high frequency instrumentation amplifier based on video-difference amplifier
• New Amplifiers Simplify Wideband Techniques - example drixing circuit for coaxial cables and twisted pair video transmission

Video switching

• Build A Video Switcher - Automatically or manually switch the outputs from up to four cameras into one video monitor, pdf file
• Printer port controls video multiplexer - four-channel computer controlled video-signal multiplexer for video frequencies as high as 300 MHz
• Remote Controlled AV Switch with S-Video, Composite Video, and Audio
• S-Video Source Selector
• Video Switch - switches RGB signals between two genlocked cameras, also available in zipped packet from Circuit Cellar April 1999

Video transmistters

NOTE: Using a video transmitter circuits described below to transmit video through air is illegal in many countries.

• 2.4 GHz FM ATV - a project concept - how to modify consumer wireless vidoe link devices
• Audio/Video Transmitter Link Test - information on 2.4 GHz audio/video links
• EMETTEUR Vidéo&Audio 224.5 MHz - video transmitter circuit, text in French, try automatic translation to English
• Low Cost Audio-Video Modulator and Transmitter - project report in pdf format
• The Design Of The Brookdale ATV Repeater System Exciter - uses a pair of Hamtronics model TA451 2-watt narrow-band FM voice transmitters to develop video and audio carriers on 439.250 MHz and 443.750 MHz
• TV Transmitter - allows you to send video to any television in the house, Poptronix kit circuit
• Video/Audio Wireless Transmitter - circuit diagram and project description
• Video Audio Transmitter - simple audio/video transmitter with a range of 3 to 5 metres and operates at VHF (H) channel 5 TV frequency (175.25 MHz)

Video modulators

• Low Cost Audio-Video Modulator and Transmitter - project report in pdf format
• MC1374 TV Modulator Circuit - data sheet that includes example circuits, pdf format
• NTSC color TV signal encoder BA7230LS - datasheet of TV modulator chip
• TV Modulátor - This circuit uses an MC1373 to form a TV video modulator

Other video related RF circuits

• Low-cost circuit biases VCOs for cable and TV - PLLs are useful in a variety of applications, most notably cable and TV tuners
• TV antenna amplifier - covers the frequencies from 40 to 900 MHz

Equipment modifications

• An AC-3 RF Output Upgrade for Laserdisc Players - performed on a Pioneer CLD-D703
• S-Video from the A520 - plans to modify A520 Commodore Amiga TV modultor to give out S-video signal

Video conversion

Sync conversion

• A Simple Video Sync inverter circuit - takes TTL level sync from computer or video game and inverts it, uses just 7404 IC for the job
• Circuit for Generating Composite Sync from Composite Video
• Sync separator includes AGC - this sync separation circuit has a gain-control circuit that helps to stabilize the sync-separation function

S-video to composite video conversion

• S-video to composite video adapter

RGB-YUV conversion

• Do-it-Yourself VGA ro PPrPb Cable
• Luminance & Color Difference to RGB Video Converter - luminance (Y) and color components (RY, BY) video signals (YUV,YprPb) to RGB converter, design by Bill Hudson, download also video opamp component datasheet
• VGA to YPrPb converter

Conversion of RGB or component video to composite video

• Luminance & Color Difference to composite video conversion methods - block diagrams of luminance (Y) and color components (RY, BY) video signal to composite video conversion
• VGATV Version 2.0 - converts RGB from VGA to card to PAL composite video
• Video Encoder for Amstrad CPC - low quality RGB to composite video circuit based on LM1377
• Video-Standard Selection Circuit for the AD722 Using Low Cost Crystals - color succarrier clock crystal switching circuit

Conversion from composite video to RGB

• FBAS-RGB-Wandler für TFT-LCD - PAL to RGB converter circuit, text in German, try automatic translation to English
• PAL-RGB-Dekoder - PAL to RGB converter circuit, text in German, try automatic translation to English
• PAL - RGB Wandler für TFT-Monitor - PAL to RGB converter circuit, text in German, try automatic translation to English

Video signal processing

• Digital sync-tip clamping: a new approach to video-signal conditioning - digital sync-tip clamping allows an ac-coupled ADC to digitize analog video without restoring the horizontal timing
• Simple Video fader
• The KD2BD ATV AM Video Modulator - allows adjustment of video gain, vidoe bias, sync and sync level
• Video amplifiers make low-cost fader - bandwidths handle SVGA or Super Mac (up to 70-MHz) video signals without degradation, fading is voltage controlled
• Video circuit clamps under all conditions
• Video equalizer sharpens VCR images - sharpens picture images without introducing the shadows, ringing, and noise often observed with commercial video equalizers
• Video Inverter - simple one transistor circuit to invert the whole video signal
• Video Stabilizer - unit designed to remove the copy-protection from prerecorded video tapes, to allow them to be played through older televisions or making backup copies of tapes which you own, designed for PAL format
• Video Stabilizer

Computer to TV

• VGA to TV converter
• VGATV Version 2.0 - converts RGB from VGA to card to PAL composite video

Conversion cables

• Amiga to SCART Cable
• SCART RGB wiring

Video mixers and effects

• Video Effects Unit - unit provides various wipe patterns for use when video dubbing, wipes one signal to black, it does not provide mixing between two separate input signals

Video signal generating circuits

• Ein vielseitiger Bildmustergenerator - test pattern generator, text in German
• Generator provides 537 NTSC pattern - generates some useful NTSC TV picture tube test patterns
• How to generate video signals in real-time using a PIC16F84 - generating video signals in software
• PIC-Ping - the game pong using a PIC16F84, outputs audio and video to TV
• PIC-Tetris - Tetris game implemented using PIC16F84, outputs audio and video to TV
• PIC-Tock - video clock using a PIC16C61
• Telescope - use your TV screen as a basic oscilloscope display, requires no modifications to the television, bandwidth is limited to 20KHz
• Testcard Generator - provides a large range of video test patterns including a full colour Test-Card, colour bars, crosshatch, grey-scale, focus grid, colour purity patterns and more, also features a basic sine-wave audio oscillator, set at 800Hz
• VCR Pong - old classic video game with TV output implemented using PIC16C711 microcontroller
• Video Pong - a video game with software generated video signal, based on PIC16F84
• Video Test Pattern Generator - generates various test patterns for use when testing and aligning television and video equipment, designed for PAL television system
• Video Tetris - a video game with software generated video signal, based on PIC16F84

Computer video generation circuits

• SVGA Generator - circuit to generate SVGA mode video 640x480..1024x768, based on Altera CPLD, text in German
• VGA Generato - VGA 640x480 test picture generator based on PIC12C509A

Video overlay

• Video Clock Superimposer - uperimposes the time of day in the bottom right-hand corner of an existing video signal, based on PIC16C711

Digital video technology

• 24-bit RGB Video Digitizer - designed for use as the front end of a digital video processor
• Closed-Caption Decoder with serial output - based on a PIC16C71, an Élantec EL4581C sync separator, and an LM393 dual comparator
• Dirt Cheap Frame Grabber - very cheap and simple but bad quality video digitizer for PC
• Homebuilt Video digitiser - connect to BBC computer or PC parallel port
• Video digitiser and software-based PAL colour-decoding - captures television pictures from a TV set, camera, or video recorder, etc., and forwards them digitally to a computer for display, storage, or general manipulation, connects to parallel (printer) port of IBM PC

Video measurements

• Trigger circuit locks onto one horizontal line - produces an oscilloscope trigger that synchronizes the horizontal sweep to a video signal that allows you to view any horizontal line by adjusting a potentiometer
• Video Line Sync Trigger Generator - trigger your oscilloscope on specific lines in a video signal

Video circuit design tips

• Black Level Clamp for video signals - proper video signal clamping is very interesting subject
• Composite Video (NTSC/PAL) to RGB
• Inverting an Analog Video Signal - it is not totally trivial
• S-Video to Composite
• Sync Generators and Separators
• Video Cables
• Video: Selecting Filter Transfer Functions - to design a superior video processing system, you must choose the right type of filter transfer function for the application

Misc circuits

• PI6ATV circuits - video switchers, modulators and signal generators for amateur TV
• The KD2BD Video Operated Relay - turns on relay if there is video signal present in the input

Related pages

• Video chips
• Video technology pages