# PWM with non inverting buffer

Hi all,I have a dubt about the source/sink current of a buffer... I want to use a PWM signal from a microcontroller with low sink/source current to drive a non iverting buffer that allow to give more current at my pwm signal for drive another logic(for example a gate of mosfet or a motor driver or simply a led)...but all non inverting buffer I seen have only sink current for HIGH of the output and source for LOW of the output..is that a problem if I drive for example a motor driver with sink current insted source current? Thanks in advice

Two transistor solution: Invert the inverter. Or do it in software.

but what is the utility of a buffer like this : http://www.fairchildsemi.com/ds/NC/NC7SZ125.pdf if it source at Vlow and sink at Vhigh how can I drive a led for example?

I think that the load (LED+resistor) could be placed between the Output and +V or Output and Gnd. In the case of the former, when the Input is High then the LED will be On, but with regard to the latter it will be Off. What's the trouble? Either way though, "50mA" isn't a "motor driver" situation.

the problem is that if I connect OUTPUT -> resistor -> LED (A to K) -> GND this circuit is crossed by current only if there is a d.d.p. between OUTPUT and GND so only if OUTPUT is HIGH but in this case the circuit is only sink current and not source so the led is turn OFF yet.

geppou: the problem is that if I connect OUTPUT -> resistor -> LED (A to K) -> GND this circuit is crossed by current only if there is a d.d.p. between OUTPUT and GND so only if OUTPUT is HIGH but in this case the circuit is only sink current and not source so the led is turn OFF yet.

Could you put that another way?

And what is a "d.d.p."?

with d.d.p I mean voltage difference...sorry

I solved!! this rappresentation that Voh has a negative current and Vol has a positive current is only a reference but mean that the OUTPUT can sink and source, in this case, 24mA continuously...I compare that datasheet of atmega328 that we know that any pin can sink and source 20mA and Voh is rappresented with negative current and Vol with positive current! Thank you anyway !!

Which is, I think. just what I told you in Reply No 3 – and then you wanted to go down the garden path.