Forums

Composite video amp

Started by bitrex October 6, 2020
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
On 10/5/2020 11:48 PM, bitrex wrote:
> 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
Differential gain and phase error, rather
bitrex wrote:

===============--
> 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? > >
** The uA733 fits your spec, Digikey have lots in various paks inc SMD. The data sheet says it hails from 1970, so maybe a bit old hat for you. I know it cos there are a couple in my 50MHz dual trace scope providing most of the vertical gain. .... Phil
On 10/6/2020 5:32 AM, bitrex wrote:

Dual-boot Linux and Windows can't figure out what time it is :(
On 10/6/2020 12:22 AM, Phil Allison wrote:
> bitrex wrote: > > ===============-- >> 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? >> >> > ** The uA733 fits your spec, Digikey have lots in various paks inc SMD. > > The data sheet says it hails from 1970, so maybe a bit old hat for you. > > I know it cos there are a couple in my 50MHz dual trace scope providing most of the vertical gain. > > > .... Phil > > > >
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." <https://www.mouser.com/datasheet/2/294/NJM2561_E-1375659.pdf> 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: <https://www.edn.com/save-3-db-of-output-power-using-feedback-to-set-the-output-impedance/>
On 10/5/2020 11:48 PM, bitrex wrote:
> 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
Neat, Linear/AD actually makes the thing I need all integrated into one chip, a 3-input video multiplexer + line driver: <https://www.mouser.com/ProductDetail/Analog-Devices/LT6559CUDPBF?qs=hVkxg5c3xu%2FSkXiqmdItxQ%3D%3D> not much more than $1 in quantity, surprisingly.
On 2020-10-06, bitrex <user@example.net> wrote:
> On 10/6/2020 5:32 AM, bitrex wrote: > > Dual-boot Linux and Windows can't figure out what time it is :(
Set both to use the hardware clock as GMT -- Jasen.
bitrex = a complete dope wrote:

==================================
 Phil Allison wrote:

>> > > ** The uA733 fits your spec, Digikey have lots in various paks inc SMD. > > > > The data sheet says it hails from 1970, so maybe a bit old hat for you. > > > > I know it cos there are a couple in my 50MHz dual trace scope > > providing most of the vertical gain. >
.
> > Amazing it's still being made and in relatively large quantity,
** Must be very special - right ?
> problem is it's not really suitable for use as a buffer amp/line driving. >
** Read you own post - fuckhead. What does it say about buffering a low impedance? ( Wot a vile, pathetic cretin ) ..... Phil