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Design >> Analog Design >> 3.3V opamp design with 1.8V devices
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Message started by rampat on Dec 27^th, 2010, 5:06am

Title: 3.3V opamp design with 1.8V devices
Post by rampat on Dec 27^th, 2010, 5:06am

Hi All

I need to design a opamp with 3.3V supply and only 1.8V devices are available from the process.How to take care of the reliability issues for the devices? If anyone knows solutions or any reference/papers to the above problem it will be a great help.

Thanks
rampat

Title: Re: 3.3V opamp design with 1.8V devices
Post by rfmagic on Dec 27^th, 2010, 7:29am

Telescopic configurationד seems the right choice for you as each transistor will take on some of the voltage to lower the stress form the 1.8V devices. On top of that you can get more gain due to the increased ouput impedances of the stacked stages.

Title: Re: 3.3V opamp design with 1.8V devices
Post by AnalogDE on Dec 30^th, 2010, 1:22am

You may also want to look into using a level shifter or regulator to level shift the supply down to around 1.8V.

Title: Re: 3.3V opamp design with 1.8V devices
Post by nus_lin on Jan 15^th, 2011, 7:02pm

the key point here is to design your circuit and set proper operation condition so that none of the Vgs or Vgd exceeds 1.8V, because the gate oxide is the most vunerable part. for diodes, the breakdown voltage should be larger than 3.3.

Title: Re: 3.3V opamp design with 1.8V devices
Post by thechopper on Jan 17^th, 2011, 4:47pm

As rfmagic suggested cascodes are the way to go, always taking care of not creating VGs voltages higher than 1.8v.
That way the 3.3v max operating voltage will be always split among at least to devices in series.

Best
Tosei