high current unity gain buffer !!

[Matrix]

Hi all
i have a trapezoidal wave of about 150ns rise n fall times with DC
voltage built into it. i want to remove the DC from the signal and
buffer it or amplify little bit (say 1.4 or 1.5 gain) without being
distorted. i have two such lines with signals 180 deg out of phase.
when i feed these signals into xDSL line driver/Buffer LT1794
then one line is distorted very much while the other is affected
slightly. then i have to transmit these signals on a twisted pair
differential bus.
1. How to remove DC from the signal, simply adding a cap does not
symmetrically shift the wave about 0V line. (or x-axis).
1. Please someone guide me about how to buffer/amplify that trapezoidal
signal without being distorted for providing about 400 to 500mA current
as a maximum.
2. and then how to get connected to the bus to transmit for a short
period of time and then be disconnected for the rest of the time.
thanks a lot.

 

[Winfield Hill]

Matrix wrote...

i have a trapezoidal wave of about 150ns rise n fall times with DC
voltage built into it. i want to remove the DC from the signal and
buffer it or amplify little bit (say 1.4 or 1.5 gain) without being
distorted. i have two such lines with signals 180 deg out of phase.
when i feed these signals into xDSL line driver/Buffer LT1794
then one line is distorted very much while the other is affected
slightly. then i have to transmit these signals on a twisted pair
differential bus.
1. How to remove DC from the signal, simply adding a cap does not
symmetrically shift the wave about 0V line. (or x-axis).

You can inject currents into the LT1794's summing-junction nodes.

1. Please someone guide me about how to buffer/amplify that trapezoidal
signal without being distorted for providing about 400 to 500mA current
as a maximum.

Are you driving a transformer? DC currents could be a problem.

2. and then how to get connected to the bus to transmit for a short
period of time and then be disconnected for the rest of the time.
thanks a lot.

Will the LT1794's shutdown / disconnect capability suffice?
Or is the part's 10us off and 2us on delay too much?

 

[Matrix]

What do you mean by summing junction diodes ?? Do you mean the
conventional inputs (pins 3,4 & 7,8) and i should inject the current
instead of voltage !!

YES, i have to drive an isolation transformer before i could transmit
anything on the bus. What should i do to cater for the DC currents.

i am not shutting it down rather i have biased it permanently for 10mA
current.
Thanks.