# Is a bootstrap capacitors always required for mosfet drivers?

I am designing a H-bridge to drive a motor that is running at 12V / 3A.

To prevent shoot-through I decided to select a IC with integrated dead time - IR2111.

What I got so far is the following circuit (showing just one half of the full bridge to conserve space): What I am curious about is the need for the bootstrap capacitor between $V_B$ and $V_S$ and the diode as shown in the datasheet:

My understanding is that usually the drain of the high-side MOSFET is connected to a much higher voltage as the supply voltage for the IR2111. To switch the MOSFET a higher voltage has to be generated, therefore the bootstrap capacitor.

But in my case the voltages (drain of the hide-side mosfet and supply voltage of the IR2111) are all 12V. So the voltage is high enough to switch the high-side MOSFET and I do not need the bootstrap capcitor. Am I right?

• Why do you put D1 and D2? The MOSFETs already have internal body diodes. Oct 29 '14 at 10:13
• @hkBattousai Body diodes are not optimized for the task. However, if you're going to take the effort to add external diodes then 1N400x diodes are certainly not the diode you should be using and is just putting that extra effort to waste. Use one suited for the task. Jun 24 '19 at 16:39