Mosfet Gate driver Circuit for inverter

BobTPH

Joined Jun 5, 2013
2,499
Why would you want to? The purpose of a gate driver is to supply a large current to the gate for fast switching, typically 1A or more. An LM324 can supply, maybe, 20 mA.

Bob
 

ronsimpson

Joined Oct 7, 2019
824
There are real gate drivers. These are fast and can push amps of current on the edges.

Most op-amps get slow and sticky when driven to the supply rails. The LM324 can only do 20mA (more or less).
 

TeeKay6

Joined Apr 20, 2019
572
Can I include an external transistor to increase the amperage?
The LM324, in addition to not having high drive capability, also has a very low slew rate (it's slow), making it a very poor choice as a gate driver. Yes, you could place a transistor stage (common emitter only) between the LM324 and the gate, using the transistor to pull the gate to 0V and using the collector resistor to pull the gate high...but you won't get very high speed that way. You could also drive a real gate driver with the LM324 and--provided you don't want to switch at a very low frequency--drive a gate from the gate driver. None of those schemes is good; the LM324 is simply too slow to drive a MOSFET gate in any inverter operating at a reasonable speed. Unless you only need to switch at 50-60Hz, don't use the LM324 to drive a gate.

UPDATE: I think everyone assumed that by "inverter" you meant a high-speed inverter as in a switching power supply. If you simply need logic inversion and the speed doesn't much matter, then other options, including the common emitter buffer that you show, would be possible. So...what kind of inverter do you need?
 

Thread Starter

Miracletech

Joined Nov 15, 2019
125
Ok. That means the circuit arrangement will be from:
AMPLIFIER - GATE DRIVER - CIRCUIT. Right? By the way, thanks for the recommendation.
 

Papabravo

Joined Feb 24, 2006
14,241
Ok. That means the circuit arrangement will be from:
AMPLIFIER - GATE DRIVER - CIRCUIT. Right? By the way, thanks for the recommendation.
As always - you should check the datasheets to determine how much base current you need to supply to get the required collector current. If 20 mA is the max current your amplifier can supply then you'll need a gain of 100 to get from 20 mA to 2A.
 
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Papabravo

Joined Feb 24, 2006
14,241
As always - you should check the datasheets to determine how much base current you need to supply to get the required collector current. If 20 mA is the max current your amplifier can supply then you'll need a gain of 100 to get from 20 mA to 2A.
Looking at the datasheets I don't think a gain of 100 would be reasonable for those transistors. Looks like something in the neighborhood of 20-40 so maybe we need to consider alternatives. You could get more gain using a Darlington Pair, but you would need two diodes in each leg to compensate for the 1.4V Vbe drop, Or you could keep searching for transistors that can switch the MOSFET gate with a smaller current than 2A.
 
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