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Need help for Designing High Frequency AC switch usingMOSFET

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Newbie level 5
Oct 8, 2009
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Hello Guys,

I am here again for AC switch only.

I have used TRIAC for AC switching but the requirement is High Frequency AC Switching, which can be achieved by using MOSFET.

So can anyone help me in designing AC switch using MOSFET?

What's "high frequency" in your opinion? kHz, MHz, GHz? Also, what's the involved voltage and current level?

Re: Need help for Designing High Frequency AC switch usingMO


See IR site for application note on how design a AC mosfet switch

All the best


The microcontroller specialist

Hi FvM,

It will be in KHz and Voltage: 9-15V, Current: 1-1.5Amp.

Basically this is for Ultrasonic Transducer, so needs to generate Frequency for Ultrasonic Transducer (Using AC Voltage).

Input and Output will be 230V AC. But at intermediate stage input will stepped down to 9-15vAC and regulated and will be given to MOSFET.

If you can guide me about Transformer Rating/Design (for Input transformer & Output Transformer) then it will help me a lot.

Your specification seems to require an inverter rather than an AC switch. An inverter usually involves a DC bus.
Furthermore, the role of the 230 V output circuit is completely unclear.

You may want to post a detailed block diagram with some explanations.

Yes, You are right its like inverter only.

But inverter gives 230v AC at 50/60Hz, where I need 230v AC in KHz for High frequency generation (For Ultrasonic Transducer).

Hi.. friends

I really need your sugesstion and comment;

If anybody familiar with 2SK3748 Mosfet. Actually I want to use these mosfet for High Voltage High frequency with HCPL 3120 single optocoupler as a driver. It means that each MOSFET, 1 optocoupler.I try to connect as H-Bridge but I cannot get the output voltage as needed(Bipolar square wave). Is it possible for HCPL 3120 and 2SK3748 use for this application. If any body know what is a suitable driver for 2SK3748 or other MOSFET can be used for high voltage high frequency.

Thank You Very Much.

I have the similar problem. I need to driver a mosfet with IC IR2110. But I dont know if is it possible for 3.5mhz???

Thanks for your answer


Maybe I missed something, but for the ultrasonic case with H-bridge, with not use two HV half bridge drivers (or a HV full bridge driver). As your frequency is not very high (20kHz range), you may consider latest generation of IGBT when using over 300V DC bus voltage.

For "fsabras", When this is for an RF amplifier (radio amateur use or ISM), it will be difficult to find a driver.

You may visit:
At the end of the page they have application notes on high power high efficient RF amplifiers.

Hi fsabras,
I think the 3.5 MHz is for that component a illusion...
Refer pls to datasheets Fig. 28...34: the basic junction temp rises from 25 Celsius/10KHz to ca 40C/100KHz,
than to min.80Cels...>>150Cels. depending of FETs & voltages by 1 MHz! :-(...

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