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[SOLVED] Duty Cycle voltage increase

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Michael Gimon

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Hello, I'm hoping someone can point me in the right direction. I'm making a square wave that can change its duty cycle. The voltage ranges from 0 to 3.75 volts but i need it to range from 0 to 5 volts. I've tried using a non inverting op amp to get that extra gain i need to achieve 0 to 5 volts but its not working. Is it something I'm doing wrong or is another type of circuit needed for a duty cycle voltage increase?


non-inverting op amp.JPG
 

kabeer02

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Well we dont know how you design your circuit but their are many pwm chips that can do that as well
 

FvM

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I agree that it doesn't make much sense to use an OP amplifier as digital level converter.
In case you want though, the OP must provide rail-to-rail output swing, LM358 doesn't.
 

Michael Gimon

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I agree that it doesn't make much sense to use an OP amplifier as digital level converter.
In case you want though, the OP must provide rail-to-rail output swing, LM358 doesn't.

assuming a rail to rail op amp is used, it can be done? Is there a different circuit that could do the job better/cheaper?
 

ZekeR

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assuming a rail to rail op amp is used, it can be done?

Yes. However, op-amps are built to handle analog signals, not digital signals--for this reason, they are pretty slow at handling digital. But yes, it can be done.

Is there a different circuit that could do the job better/cheaper?

Yes. Use a 2N7000 transistor with a 10kOhm resistor attached from its drain to +5V, and its gate attached to the 0=>3.75V digital signal. The 0=>5V signal will appear at its drain. A caveat is that your digital signal will be inverted.

If you don't have a 2N7000, you can use a 2N2222 or 2N3904 in a similar fashion. Attach a 10kOhm resistor from its collector to +5V, and a 10kOhm resistor from its base to the 0=>3.75V digital signal.
 

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Is there a different circuit that could do the job better/cheaper?
A digital logic gate with TTL to CMOS level conversion capability, e.g. 74HCTxx, or a comparator.
 

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