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1,700 Views 1 Replies Last post: Dec 17, 2009 4:05 AM by Michael Kellett RSS
Vipul Panchal Newbie 3 posts since
Dec 16, 2009
Currently Being Moderated

Dec 16, 2009 2:36 PM

How to design high votage amplifier?

Hi,


I need to design an amplifier for 100KHz, 5Vp-p square wave amplifed to 50Vp-p signal with zero crossing (i.e. +25v to -25V)

I am thinking to use OPA2544 Op-amp from TI/Burr-brown with +/-27V supplies. I have attached the circuit here, I do not simulation tools to simulate it.

could any body verify the circuit and post the suggestions?

schm.JPG

Michael Kellett Apprentice 40 posts since
Oct 3, 2009
Currently Being Moderated
1. Dec 17, 2009 4:05 AM in response to: Vipul Panchal
Re: How to design high votage amplifier?

This part will not do what you want.

 

Check the data sheet carefully:

 

The gain bandwidth product is only 1.4MHz - this means that the open loop gain will be only 14 at 100kHz and 1.4 at 1MHz - you are trying to amplify a square wave at 100kHz which means that if you want it to look halfway reasonable on a scope you need a closed loop bandwidth of 1Mhz. You should be looking for an amplifier with a gain bandwidh product more like 1MHz * (10 for the open loop gain) * 10 (for some feedback) - ie a gain bandwidth product of 100MHz !

 

Your output should be a sqare wave wih 50V pp amplitude at 100kHz - if you allow the rise and fall times to be 10% of the period that means that your output must slew 50V in 1uS - so the slew rate of your chosen chip must be at least 50V/uS but the OPA2544 only offers 8V/us.

 

The data sheet also shows that the output can only get within 4.2V of the supply rails (at 0.5A output current) so a sensible design margin would be 5V which means you should use +/-30V supply rails.

 

You don't need simulation tools to choose a part - just check the basics.

 

When you are ready to simulate you can get a free (and good) simulator from Linear Technology (LT Spice IV on www.linear.com).

 

If you explained what you need the output to do it might be possible to advise you better.

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