buffer doubt

[ramu01]

hey ppl

i have a USB web cam. so it it has data+ and data- connections for USB communication

when i tried to give the data+ connection through a buffer (opamp- voltage follower), the computer says "device error". without any buffer, its working fine.

the thing is when i connect through the voltage follower, the voltage output at Data+ terminal of the webcam gets altered !!

why is it so ? voltage follower should suppose to give the same voltage right ??

 

[Mikebits]

USB is digital.

 

[Nigel Goodwin]

So far you've asked three questions, none of which make any sense as you give no context for them, but from what you've asked you obviously have no idea what you're doing.

 

[ramu01]

USB is digital !! yep, i know that !!

what does digital mean ? after all it s discrete with respect to time. analog is continuous. thats the only difference!!

now does this anyway related to the property of an operational amplifier? though the signal is discrete, voltage follower is supposed to follow the input voltage eh ??

 

[ramu01]

and Mr.Nigel goodwin what context you expect to make those ques sensible ?? i have clear idea of what am i doing. and i ve asked for some solutions to the problems i am facing through those ques. and if you dont ve the answer, dont just post reply for the sake of replying !!

 

[Nigel Goodwin]

and Mr.Nigel goodwin what context you expect to make those ques sensible ?? i have clear idea of what am i doing. and i ve asked for some solutions to the problems i am facing through those ques. and if you dont ve the answer, dont just post reply for the sake of replying !!

No one can answer your questions because they don't make any sense without context, you need to tell people what you're trying to do, and why you're trying to do it that way. If you had a clear idea what you were doing you wouldn't be trying to feed a USB camera though an opamp!.

 

[Mikebits]

Digital has fast rise and fall times, most analog parts are too slow and round the edges amongst other issues.

 

[ramu01]

alright ..

well, all that i am trying to do is "wireless transmission of video signal from a USB camera" !!

i have a USB web cam. Now it has a CCD sensor .. and it sends digital clocked signals at 32 frames/sec

so in order to transmit this signal, i ve to modulate it with a high frequency carrier signal. that is instantly add (merge) the camera signal with the carrier signal. then transmit the resultant signal through an antenna.

in the receiver side, i would receive this modulated signal through an antenna. i would generate the same carrier signal in the receiver side too. and i would subtract this carrier signal from the received modulated signal, so that i could get back the camera signal..

then i could feed this demodulated signal to the computer through the USB port..

 

[ramu01]

analog is very slow !! so what am i supposed to use for the digital signal ?

 

[Mikebits]

alright ..

well, all that i am trying to do is "wireless transmission of video signal from a USB camera" !!

i have a USB web cam. Now it has a CCD sensor .. and it sends digital clocked signals at 32 frames/sec

so in order to transmit this signal, i ve to modulate it with a high frequency carrier signal. that is instantly add (merge) the camera signal with the carrier signal. then transmit the resultant signal through an antenna.

in the receiver side, i would receive this modulated signal through an antenna. i would generate the same carrier signal in the receiver side too. and i would subtract this carrier signal from the received modulated signal, so that i could get back the camera signal..

then i could feed this demodulated signal to the computer through the USB port..

Well there is the problem. USB has NRZI data. You just cannot recover the data from the RF by just demodulating and recovering the data. You have to make the data back into NRZI.

 

[ramu01]

sorry, couldn't clearly get you . if you dont mind, can you please explain me to a better extent ..

 

[ramu01]

tell me what point should i exactly start with to come up with this "wireless video transmission" ..

 

[Mikebits]

For a start you can look here. https://en.wikipedia.org/wiki/Non-return-to-zero
A ways down explains NRZI. I am too tired right now to be much help. I think I am going to sign off.

 

[ramu01]

will feel great if you could send me some suggestions later when you re free !! thanks !!

 

[Nigel Goodwin]

Isn't USB a two way process as well?, you can't just connect it to a transmitter, nor does the transmitter have the high bandwidth required even if you could.

 

[Mikebits]

Nigel is correct, the USB is a half duplex link. There are single chip solutions for wireless USB but they are not trivial to use.

**broken link removed**