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AD8139 spice model rails?

Question asked by vazine on Jan 12, 2012
Latest reply on Jan 12, 2012 by charlyelkhoury

Hello,

 

I am interested in using the AD8139 as an RF-switch driver since it's supposed to get <11ns switching speeds. The design is detailed here: www.edn.com/contents/images/10605di.pdf

I am trying to get the swing as close to 0V and -5V as possible to optimize performance in some high speed RF switches. The AD8137 spice model works well for me in comparison to its datasheet, but the AD8139 model can't seem to output any voltage lower than -4V with Vee = - 5V. I believe the AD8139 will be the better option for me as I do not require low power, would benefit by the better rail-to-rail specs, and the speed.

 

Is this simply an error with the spice model or am I using it wrong? The AD Diff-Amp Calculator shows the rail to be much closer to -5V as advertised in the datasheet. I am using the subcircuit model in LTspice.

 

Thank you,

 

Eian

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