pre emphasis with voltage mode driver

[sharas]

Hi,

I want to implement a "pre-emphasis" feature in my voltage mode driver, but I can't see, to do so without violating the output impedance requirement. Does anyone have an idea?

Thanks,


Sharas

 

[dick_freebird]

If you looked at output impedance Norton style that would
suggest you want two controlled currents, summed. One
drops out after the peaking dwell. The other is closed
loop controlled to get the right voltage across the output
impedance. This could be longer term or real time.

In a voltage driven, voltage feedback scheme you'd probably
prefer to put the peaking before the power amp.

 

[sharas]

Thanks dick_freebird.

But doesn't that chnge the output impedance during operation (a thing that I would like to avoid in order to prevent reflection from the line)?

Thanks,

Sharas

 

[dick_freebird]

If your current sources are true current sources, then
they have an infinite output impedance and no change
to the port impedance (that would be set explicitly by the
Norton resistor). Of course real ones are not ideal,
but "close
enough" can be had.