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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Jester on August 19, 2021, 09:15:02 pm

Title: Ampliifer 5ns rise time 300V p-p
Post by: Jester on August 19, 2021, 09:15:02 pm

How difficult would it be to design an amplifier capable of 5ns rise times with an output of 25V p-p, 100V p-p and 300V p-p?

The output to drive an ultrasonic transducer over RG59

Title: Re: Ampliifer 5ns rise time 300V p-p
Post by: Jay_Diddy_B on August 19, 2021, 09:24:05 pm

Hi,

It is hard to do. If you just consider capacitance.

I = C dv/dt

dv/dt = 300 / 5E-9 = 6E10  V/s

assume C= 10pF

I = 10E-12 x 6E10 = 0.6A

0.6A x 150V = 90 VA

that is a lot of current to drive just 10pF.

Regards,

Jay_Diddy_B

Title: Re: Ampliifer 5ns rise time 300V p-p
Post by: Marco on August 19, 2021, 09:39:56 pm

Given the coax, presumably the piezo is 50 Ohm matched.

So now you just have to make ~100 MHz 1kW class E amplifier.

Title: Re: Ampliifer 5ns rise time 300V p-p
Post by: Jester on August 19, 2021, 09:48:20 pm

The existing system (not performing well, but working) is with amplifier that outputs 15Vp-p, 8ns rise time. Perhaps doubling to 30Vp-p might be a more realistic goal?

Title: Re: Ampliifer 5ns rise time 300V p-p
Post by: Marco on August 19, 2021, 10:18:12 pm

Would a LMG1210EVM suffice? Or does it need to be a sinewave?

Title: Re: Ampliifer 5ns rise time 300V p-p
Post by: ejeffrey on August 20, 2021, 03:41:48 am

Sin wave, square wave, or other? Fixed frequency or variable?  How long is the cable and what is the piezo capacitance?  How accurate does the amplitude have to be and what is your tolerance for reflections.

If you just need a square wave drive mosfet switches will do this fairly easily.  If you want a sine wave you can add an inductor to make the piezo resonant and make it much easier to drive.