open collector question

I have an open collector toggle signal, instead of get on/off at 24 volts and grnd, I would like to get -12v to +12v, I am not an electronics guy but with a little knowledge in the field, could anyone tell me how to do this? Great thanks in advance for any posts..

I have an open collector toggle signal, instead of get on/off at 24 volts and grnd, I would like to get -12v to +12v, I am not an electronics guy but with a little knowledge in the field, could anyone tell me how to do this? Great thanks in advance for any posts..

That's a good question. It's been a long time since I designed a transistor circuit and I wasn't all that good at the time.

Maybe a Class B, push-pull circuit would work. Look at just the transistor part of these circuits, for example:

If you described the problem more precisely, you might get some experts to answer.

So, you have a 24V supply, an open collector output tied to the +24V via a resistor and you want this to become -12V to +12V relative to ground? What's the toggle signal hooked to? How fast does it operate? What will it be hooked to? Do you have access to any other supply rails?

In other words, can you describe the situation more completely?

Jon

I'm assuming your open collector transistor has the emitter at ground, in the middle of your +/-12 supplies. If so, then one easy solution is to connect the base of a PNP device to the open collector through a current limit resistor... try 10k for starters. Connect the emitter of the PNP to +12, and the load on the open collector can go to -12 (or gnd... anything lower than +12). If for some reason you really need an NPN open collector on -12 pulling from +12. just continue this trick and feed the PNP collector through a resistor to the base of the NPN.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Hi, Gary. The first thing you're going to have to do is get +12V and

-12V supplies. You can get the +12V from the +24V with an LM7812, a positive 12V regulator, like this (view in fixed font or M$ Notepad):

| ____ | +24V | | +12V | o----o----|7812|----o-----o | | |____| +| | --- | --- | --- | --- | .1uF| | 10uF| | | | | | o----o------o-------o-----o | GND (created by AACircuit v1.28.6 beta 04/19/05

Now for the negative voltage, you can use a 555 as a voltage inverter like this:

| | +12V +12V +12V | | + + | .-. | | | | |24K .---o----o---. C = 100uF 25V | | | | 8 4 | D = 1N4002 | '-' | | C | | | | | o-----o7 | +|| D -11.3V | | | 3o---||--o----|