LM339 Sink to Source Converter??? - Electronic Circuits Projects Diagrams Free

**Krumlink** · 6th January 2008, 10:45 PM

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 · 7th January 2008, 12:30 AM

Quote:

Originally Posted by 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

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** · 7th January 2008, 01:49 AM

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** · 7th January 2008, 11:09 AM

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

**Krumlink** · 7th January 2008, 07:01 PM

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** · 8th January 2008, 01:09 AM

Quote:

Originally Posted by 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

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

**Krumlink** · 8th January 2008, 04:57 AM

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

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6th January 2008, 10:45 PM	(permalink)
Krumlink	LM339 Sink to Source Converter??? 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 __________________ MechTronics World of Warcraft is a disease

7th January 2008, 01:49 AM	(permalink)
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 __________________ MechTronics World of Warcraft is a disease

7th January 2008, 11:09 AM	(permalink)
Nigel Goodwin	Use an opamp rather than a comparator - perfect cure in one easy step!. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

7th January 2008, 07:01 PM	(permalink)
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 __________________ MechTronics World of Warcraft is a disease

8th January 2008, 04:57 AM	(permalink)
Krumlink	No, it was intended for a single input at any one moment. __________________ MechTronics World of Warcraft is a disease