I need to design a totem bole bjt based gate driver for Mosfet IRF640, which is going to be used in a Buck converter.

I know the peak gate charging current= 1A.

I've already selected my complementary Bjt pairs (2N2222A,2N2907A) so it can give a max current = 0.6A.

The mosfet has a minimum \$V_{gsth}\$ = 2V and max of 4V. Now how do I select Rg? Rg = [Vgg - V(gs,Io)]/ig.

From the equation:

1.On no load, I get Rg = [15-4]/0.6 = 18.33 ohms

  1. On full load (Id=10A), V(gs,Io)=5.5V from datasheet, so Rg =[15-5.5]/0.6 = 15.84 ohms.

  2. Considering -Vgg = -5V, I get Rg = [15-2-(-5)]/0.6 = 30 ohms.

Where should I use the peak gate charging current value of 1A?

Thanks in advance.

  • \$\begingroup\$ Schematic will get you better answers. \$\endgroup\$
    – user16324
    Commented May 14, 2020 at 12:48
  • \$\begingroup\$ Clean up the formatting of your question too. It looks a mess. \$\endgroup\$
    – Andy aka
    Commented May 14, 2020 at 14:04
  • \$\begingroup\$ This is a totem-pole. You are thinking instead about a push-pull. Also see here. \$\endgroup\$
    – jonk
    Commented May 15, 2020 at 3:40


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