Change the amplitude of logic level

[bhl777]

Hi all, I have a Pwm output signal with 2.5V logic "1" from a chip, could anyone teach me if I want to change this signal to a 5V logic "1", while keeping the duty cycle unchanged, what kind of circuit should I use? Thank you! Please recommend some IC pruducts.

 

[crutschow]

You could use a comparator, such as an LM339.

Connect a 10kΩ resistor from the (-) input to common. Also connect a 30kΩ resistor from the (-) input to the 5V supply. (This sets the input logic trigger level at 1.25V.)

Connect a 10kΩ resistor from the input signal source to the (+) input. Also connect a 200kΩ resistor from the (+) input to the output. (This provides about 0.3V hysteresis to avoid any oscillations during the logic transition).

Connect a 1kΩ resistor from the output to the +5V supply.

Of course you also need to connect the LM339 supply pins to +5V and common with 0.1uF decoupling cap between power and ground.