totem pole and mosfet

Hi,
Can any body please tell me how to drive n channel mosfet with totem pole. I have to use mosfet as a switcher. PWM pulses are to be given to totem pole configuration.
thank you

Guess you mean a NMOS half-bridge topology. You'll need a level shifting gate driver for the high side FET, ICs like IR2110 provide a combination of low- and high side drivers for half bridge.

He could still use discrete (totem pole) drivers for the high-side Mosfet if he's using an optocoupler between the PWM signal and the totem-pole input.

But, as he didn't mentioned anything about a specific topology (or a high-side switch for that matter), I guess he only needs to apply the PWM signal to a simple Mosfet (like modulating a LED output or controlling a DC motor speed).

Time will tell what's his intention.

Thanx all,
As i mentioned i have to use mosfet as a switcher. I have to design DC-DC converter. Controller is PIC10f320. No driver IC can be used for driving mosfet. I have to supply PWM signal to to totempole configuration and drive mosfet from it. Normal totem pole arrangement given on internet can't be used as it will invert the signal. That's why i am confused as how to keep signal in phase which is to be given to totem pole from microcontroller with that of output.
Thank you

@djc:

Take a look at this application note:

**broken link removed**

A non-inverting totem pole circuit is quite common, actually.

thank you,
I presented the same circuit initially (without base to collector resistor), but it was discarded at the spot. Voltage required at gate should be 12-15 V. What i have been told is that circuit will give base voltage at NPN (which will be at the max 5v) from microcontroller minus 0.7V at base emitter junction. so the the maximum voltage wud be 4.3V. Which is not acceptable. That's why have to look for an alternate arrangements. please tell me, when PNP transistor is turned ON, by supplying 0v at the base, and emitter at 15V, will we get all the voltage (minus junction drop) i.e at least 14V at the collector?If it is then i can attach base of NPN transistor in totem pole configuration to collector of another PNP transistor and operate that PNP transistor with another NPN transistor operating through micro controller. similarly collector of first PNP transistor attached to base of lower PNP transistor of totem pole configuration.

The term totem-pole circuit is unfortunately vague. Traditionally it has been used for the all NPN output stage of TTL ICs, now I see it occasionally for complementary voltage followers as shown in the Zetex application note.

You finally managed to give your specification:
- non-inverting driver
- 5 to 15 V level conversion

Required gate current is yet unspecified

You need at least two transistors for the level converter, either NPN/PNP or 2xNPN. To achieve fast switching, a complementary voltage follower might be used.

Hi,

Why not using a logic level mosfet and drive it directely from microcontroller?

Klaus

Totem pole driver is only neccesary when you want very low transition time. As it's a DC-DC converter you must want that.



This circuit will not invert the original signal, and will give a high current boost. Again, with nospecific requirements, as oscillation frequency and output MOSFET characteristics, nothing can be calculated.

If your "job" is to design the -power supply- then
who's telling you that you can't use a MOSFET
driver, and why - when the majority of industry
does so? A uC can't drive any useful MOSFET
directly. A gate driver is likely cheaper and
better than any jumble of discretes and passives.
An integrated half bridge driver also relieves you
of the dead time tweaking and its variation which
will cost you way more in burnt FETs if you try
and wireball it with loose parts driving high side
and low side switches.

If they're making you learn how to do it early-'80s
style, they **** at teaching or at engineering,
or both, depending on what they pretend to be.

Logic level FETs might "work" for the low side
(sync rect) switch (aside from the gross load
capacitance and the badness of attaching it to
a uC pin - watch the drain dV/dt kick) but only
if this uC is a 5V I/O one. There's still the problem
of driving the high side switch which wants level
shifted above the VIN rail (unless you use a PMOS
which nobody who cares about cost does, outside
of integrated circuits).

Now the remark about totem pole being unsuitable
because it inverts, makes no sense and makes me
think you're in way over your head. You could just
invert the output logic sense if that's all there was
to it. It's a microcontroller and code-bits are free.

Thanx everyone for the inputs. Finally circuit will be like Bruno specified. However instead of PNP transistor before totem pole, NPN transistor will be used. Which will be driven by another NPN transistor from microcontroller. Collector of middle transistor will be joined to base of PNP transistor of totem pole and upper transistor will be driven directly from 12v supply through the resistor. It may sound confusing without the diagram. pardon me for that.