user13798: If it matters, I'm talking about the arduino uno v3.

user7856: Check out the ATMega328p datasheet: each of the 3 timer/counter blocks can generate PWM (2 PWM signals per timer) and on top of that, typically Timer1 (16 bits) is used by the OS/scheduler/whatever, unless you are really running on bare metal.
It's a limitation, but so is everything else.
If you do not like it, you can always choose a different microcontroller, either AVR or something else.
Certain models might  be designed to have more units of a specific type than you would find on generic microcontrollers.

13798: <p>If it matters, I'm talking about the arduino uno v3.</p>
 7856: <p>Check out the ATMega328p <a href="http://www.atmel.com/images/atmel-8271-8-bit-avr-microcontroller-atmega48a-48pa-88a-88pa-168a-168pa-328-328p_datasheet_complete.pdf" rel="nofollow">datasheet</a>: each of the 3 timer/counter blocks can generate PWM (2 PWM signals per timer) and on top of that, typically Timer1 (16 bits) is used by the OS/scheduler/whatever, unless you are really running on bare metal.</p>

<p>It's a limitation, but so is everything else.</p>

<p>If you do not like it, you can always choose a different microcontroller, either AVR or something else.
Certain models might  be designed to have more units of a specific type than you would find on generic microcontrollers.</p>
