2.5MHz Switching

(Assuming "24v" is not RMS or pkpk but a pulse peak height of 24V and the

VMOS?

The ICL7667 as a bridge driver with VCC=12V can do that.

regards - Henry

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"icegray" schrieb im Newsbeitrag news: snipped-for-privacy@d57g2000hsg.googlegroups.com... | Hi everybody, | I must drive a nebulizer transducer and I need 2.5MHz 24V (almost | 200-300mA). I can create 2.7MHz 5V by microcontroller but I can't | drive the fet to 24V. | I am trying use two fets, first one drives second and second one | drives transducer. Second fet can't switch after 1MHz. | Could you please recommend a circuit for 2.5MHz 24V (almost | 200-300mA)? | Thanks |

.....But at 2.5megs [---->and 300ma drive, you'd need 48V/uS slew---->] ..... to give a poor triangular output. Best to drive it as a class B amp'.

On 22 Apr 2007 14:01:13 -0700, icegray Gave us:

Hey, John... where was that 50Watt device you posted a link to?

use the FETS in common S mode., you only need the max voltage on the gate to fully saturate it. So instead of source feeding the transducer, you will be sinking the common side via the common source Fet. you simply need a 24 volt supply to feed the + rail for the transducer.

If you can use a sine wave, the solution is trivial.

Tam

You sound like a digital guy -- "... fet can't switch ...".

This should be relatively easy to accomplish with the right parts, but you have to treat it like an analog circuit. At that frequency you should be able to do it more or less like a base band amplifier with the right parts.

So:

• Get a copy of the ARRL Handbook. It will induce you to treat your circuit like it's RF, with lots of resonant circuits -- resist it, unless you can be very certain of the capacitances not changing much. Even so, the Handbook has lots of good basic analog circuit knowledge for you.

• Before you do any more work on the bench, get a copy of Spice (I like LTSpice, but you'll have to come up with your own MOSFET and transducer models). Make sure you can simulate the circuit before you build it.

• You need 7.2 watts out, unless your load is highly reactive. If you can count on 25mW out of your microprocessor pin that means you need almost 50dB of gain -- and 25mW out of a 5V pin works out to 10mA. If you assume 20dB of gain per stage of amplification that indicates that you need at least three stages.

• There may be drivers out there that can do this. It's up to you to find them, and my quick check to answer the question "what the heck is a nebulizer" indicates that maybe you want this solution to be cheap cheap cheap. Commercial power drivers usually aren't cheap, so you get back to a discrete circuit pretty quickly.