LM339 Sink to Source Converter???

[Krumlink]

I am building a secret project, codename: KAPTR v1.0, and The Comparator in it can only sink current, not source it, so therefore I need to figure out in order to get the H Bridge working for it how to convert the Sink (negative output) into source (positive output), essentially I need to invert the negative signal. Do you have any ideas on how I can approach that? I was thinking of using a PNP Transistor on the LM339 outputs and have that output a Positive signal, but would that work if I then used that as a positive output?

Thanks

 

[Papabravo]

I am building a secret project, codename: KAPTR v1.0, and The Comparator in it can only sink current, not source it, so therefore I need to figure out in order to get the H Bridge working for it how to convert the Sink (negative output) into source (positive output), essentially I need to invert the negative signal. Do you have any ideas on how I can approach that? I was thinking of using a PNP Transistor on the LM339 outputs and have that output a Positive signal, but would that work if I then used that as a positive output?

Thanks

Yes. The open collector output stage of the LM339 can be used to turn on a PNP stage. Current flows from the supply to the emitter to the collector to the motor. The base needs to be pulled up to the motor supply and a limiting resistor from the base to the LM339 output will set the maximum current through the motor.

 

[Krumlink]

Thanks a lot, was testing it and I put one on there for testing, and It works great. Thanks a lot. I just have to mount a few boards and I will post more soon

 

[Nigel Goodwin]

Use an opamp rather than a comparator - perfect cure in one easy step!.

 

[Krumlink]

Well then it would make the H bridge (that I am using) stall, because it would turn the high side and low side on at the same time, causing a stall and a short circuit, a easy way to destroy it

 

[Nigel Goodwin]

Well then it would make the H bridge (that I am using) stall, because it would turn the high side and low side on at the same time, causing a stall and a short circuit, a easy way to destroy it

So your H-Bridge is badly designed as well?.

 

[Krumlink]

No, it was intended for a single input at any one moment.