I'm planning to build a pwm driven H bridge. I have all set up, flyback diodes, pull up and down resistors on high and low on bridge's side, decoupling capacitors and so on, but I only have TIP122 Darlington BJT available at my university. I know I need a big base current to charge base capacitance as fast as possible to allow faster PWM frequencies. Unlike some FET's, it doesn't have "fast switching" written on its datasheet. But besides that, the datasheet lacks the "ON base input resistance" and the input capacitance, only output capacitance.

How can I say for sure that this BJT doesn't suits me? I'm planning using 100Hz for pwm

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    \$\begingroup\$ for 100hz suits well, but is a 100hz enough? \$\endgroup\$ – Marko Buršič Nov 9 '15 at 12:06
  • \$\begingroup\$ this is my first h bridge circuit done. I know there's some CI's for it, but I would like to test my dc motor on my on h bridge. So the low frequency. It would be a very weak RC car. Does it sound too low? \$\endgroup\$ – GabrielRado Nov 9 '15 at 12:11
  • \$\begingroup\$ TIP120/122 can work with 100Hz without any problems, even 1kHz would work. \$\endgroup\$ – ammar.cma Nov 9 '15 at 12:14
  • \$\begingroup\$ Great! I will rise to 1kHz so. But what calculations made this thought possible? \$\endgroup\$ – GabrielRado Nov 9 '15 at 12:19
  • \$\begingroup\$ Reading the datasheet for TIP122 helps, and some hands-on experience. \$\endgroup\$ – ammar.cma Nov 9 '15 at 12:42

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