0
\$\begingroup\$

As part of a radio transmitter design, a square wave oscillator has to drive a power mosfet. Given the gate capacitance and the frequency, the maximum current should be around 50mA.

The power mosfet is a little bit of an overkill (it works up to 2A), but RF mosfets don't go as high as I need, at least not the one I have. The oscillator can't source that much current, so I need a buffer that can source 50mA at 1MHz. The only buffers I know how to build are BJT followers with a common emitter, but they aren't fast enough. When switching it on and off, it takes time for it to go up to VCC again.

\$\endgroup\$
6
  • \$\begingroup\$ Try searching for "MOSFET gate driver". \$\endgroup\$
    – WhatRoughBeast
    Mar 15, 2016 at 23:36
  • \$\begingroup\$ I did, I could only find ICs that I cannot buy where I live. I could order them from Digikey or something but shipping is insanely expensive. Do you know any MOSFET driver fast enough and really popular? Some popular ICs are findable around here \$\endgroup\$
    – freejuices
    Mar 15, 2016 at 23:52
  • \$\begingroup\$ Why not build yourself a totem-pole driver with a 2N2222/2N2907 complementary pair or parallel enough CMOS gates to drive the MOSFET gate? \$\endgroup\$
    – EM Fields
    Mar 16, 2016 at 0:20
  • \$\begingroup\$ I have seen many industrial induction heating devices, but at 1Mhz there are just vacuum tubes. You won't find any ready made gate driver for that frequency, perhaps you should look in some Tesla coil builders forum. \$\endgroup\$
    – Marko Buršič
    Mar 16, 2016 at 9:57
  • \$\begingroup\$ Maybe try this? \$\endgroup\$
    – EM Fields
    Mar 16, 2016 at 10:50

1 Answer 1

Reset to default
1
\$\begingroup\$

I have done the 'roll-your own' MOSFET driver and it works well enough for frequencies below ~16kHz, but to drive at 1MHz, you will need a MOSFET driver for sure. Fast switching times will be critical and the roll-your-own method will not be adequate.

The recommendations that I'm giving are typically used for a half-bridge setup (DC-DC converters, motor drives, etc.), but should lead you down the right paths.

I have used the FAN7842MX successfully for frequencies up to 60kHz on TO-220 packages (lots of capacitance to overcome). It only has about 300mA of instantaneous gate drive current.

The IR2011 series would probably be better. It has 1A gate drive current capability.

I can't remember the part number, but there are some with higher ability to drive the circuit. At 1MHz, you need a solid gate drive.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.