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That's a mosfet driver circuit (taken from here), I understand the operation of the circuit but i don't know what the purpose of R5 is. Is it a pull-up resistor?. Also, would it change anything if i pulled the base of Q1 down to ground instead of pulling it up?

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    \$\begingroup\$ A crucial factor in how R5 operates is determined by what else is connected to it and the base of Q1. Without knowing all the details of what else is connected, it is anyone's guess what R5 does. \$\endgroup\$ – Bimpelrekkie Apr 14 '17 at 13:45
  • \$\begingroup\$ @FakeMoustache I will connect it to a PWM signal from a microcontroller. Is that what you mean? \$\endgroup\$ – iMohaned Apr 14 '17 at 13:56
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    \$\begingroup\$ I looked up TL494. The datasheet specifies C1 and C2 as "Collector terminal of BJT output 1" (and output 2, correspondingly). ti.com/lit/ds/symlink/tl494.pdf \$\endgroup\$ – Dampmaskin Apr 14 '17 at 13:57
  • \$\begingroup\$ @Dampmaskin aha! so it depends on the output stage of the circuit connected to the base of Q1, right? \$\endgroup\$ – iMohaned Apr 14 '17 at 14:01
  • \$\begingroup\$ Yes, in order to say something about the workings of the circuit around Q1, we need to know that whole part of the circuit, and that includes the output stage of the TL494. \$\endgroup\$ – Dampmaskin Apr 14 '17 at 14:06

The TL494 has an open-collector output. Without R5, Q1 won't turn on.

If you want to pull it down, you need a something to turn the transistor on with and I'm not sure that TL494 accepts voltages higher than GND on the emitter pin, you might need to look for another solution. A push-pull output driver for example.

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