Looking for a recommendation for a voltage-feedback op amp suitable for buffering/amplifying composite video signals, not a portable application so +5/-5 supply is OK. An amp that can drive 75 ohms directly is nice but not required I can always add a buffer. Something around $1.50 in quantity?
There's a lot to choose from and not everything lists differential gain and differential phase up-front so a recommendation would be nice
Wow, magnetic tape or disc-file systems. I'm picturing one of those big cabinets with spinning tape mass storage for mainframe computers.
Amazing it's still being made and in relatively large quantity, even. All transistors inside look to be NPN, maybe the design dates from the time when it wasn't cheap to put PNPs on an IC. problem is it's not really suitable for use as a buffer amp/line driving.
I just noticed NJR seems to make a bespoke chip for that "and is suitable for low power design on downsizing of Car camera and CCTV."
and includes the 6dB voltage gain to compensate for the termination divider action.
The application is something like that, buffering the output of a video multiplexer into an isolation transformer. There's an EDN article on how to set the output impedance using feedback rather than in-line resistance but needs an op-amp type of amplifier that can have arbitrary gain:
Analog Devices make Op-Amps for HD TV that drive coax with over 350 MHz ban dwidth. I have some Grass Valley and some Extron video DAs that use them. I can pull one to get the part numbers, if needed. I can't access my externa l drive with my design notes right now. I'm still having electrical problem s. That computer is on a circuit that was fried. I convert the video DAs to 50 ohm for 10MHz DAs
Yeah a list of any part #s would be nice, though AD products sometimes tend to break the bank :)
I was pretty surprised this thinger is only $1 in quantity. I need to multiplex several signals and drive a cable and it fits the bill:
300MHz bandwidth is probably overkill for standard def composite but it's hard to argue with the price. Honestly lots of inexpensive op amps have what it takes in theory for the bandwidth and output drive to do the job for standard-def composite but the ones that do it well have low differential gain and phase error
bandwidth. I have some Grass Valley and some Extron video DAs that use the m. I can pull one to get the part numbers, if needed. I can't access my ext ernal drive with my design notes right now. I'm still having electrical pro blems. That computer is on a circuit that was fried. I convert the video DA s to 50 ohm for 10MHz DAs
As a Broadcast engineer, I was thrilled when RCA introduced a first real vi deo amplifier for NTSC video in 1988. It was flat to 5 MHz, and it could dr ive 75Ohm coax. All for $10 each, if you could even buy them. A Broadcast D A was over $1000, per channel, with four outputs. That was what Grass Valle y started the company with, Video DAs. They eliminated having to loop every thing on one output. You had seperate feeds for the transmitter, master mon itor and two others to drive less critical loads. No one liked going off ai r to exchange equipment when a monitor died, in a long loop. They also made DA's for synce signals and Chroma.
One thing that doesn't seem easy to find at reasonable cost nowadays is a synchronization/"black burst" signal-generator chip. That e.g. just generates the NTSC composite timing pulses but no luminance or chroma so you get a black raster.
The LM1881 is still made but the LM1882 looks to be gone. The '1881 can strip the video from a composite signal if you already have it but doesn't look like it can generate the sync itself.
Renesas does make a cheap chip that can generate the frequencies you'd need for different standards from a clock by fractional PLL but you'd need some external logic to make a black burst:
Hz bandwidth. I have some Grass Valley and some Extron video DAs that use t hem. I can pull one to get the part numbers, if needed. I can't access my e xternal drive with my design notes right now. I'm still having electrical p roblems. That computer is on a circuit that was fried. I convert the video DAs to 50 ohm for 10MHz DAs
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l video amplifier for NTSC video in 1988. It was flat to 5 MHz, and it coul d drive 75Ohm coax. All for $10 each, if you could even buy them. A Broadca st DA was over $1000, per channel, with four outputs. That was what Grass V alley started the company with, Video DAs. They eliminated having to loop e verything on one output. You had seperate feeds for the transmitter, master monitor and two others to drive less critical loads. No one liked going of f air to exchange equipment when a monitor died, in a long loop. They also made DA's for synce signals and Chroma.
I have a Tektronix TSG170A NTSC Television Sync Generator.I bought it when NTSC died for broadcasting. I also have some Tektronix Waveform Monitors an d Vector Scopes. I will try to get those IC numbers, later today. I think o ne of the Grass Valley rack mount systems is where I can get to it.
The TSG170A looks relatively modern and expensive enough that it might be synthesizing all the signals from a microprocesor....
"The Tektronix TSG170A NTSC Television Generator offers you the test signals you need plus the advantages of master- and genlock-sync capability. It provides true 10-bit digital signal accuracy with a full complement of test signals and a stable master sync generator."
Fast 10 bit DACs are definitely cheaper than they used to be, too
It was $41 on Ebay. The first Sync Generator that I used was RTL based, and built by Grass Valley in the early '70s. It was monochrome only, but I sti ll managed to transmit a slide with color. The station got it, when the rec eived their Distribuition Amplifiers. They were given a new transmitter by AFRTS, and the DAs eliminated the need to change video cables when switchin g transmitters. The Sync generator was a dual system with genlock and autom atic fall over upon failure.
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