How to pull up a voltage?

Dear Kevin,

one of the ways is to use a pull up resistor. Also, you will need to calculate how much current your applicaiton can source (derive the load resistance).

Simple Example will be:

http://en.wikipedia.org/wiki/Pull-up_resistor

Hope it helps

Cheers

Edmund

Hi Kevin,

Your question doesn't look very clear to me, are you asking how can you step up a -1Volt to 1Volt supply, such that it is a 0Volt to 2 Volt Supply?

If so, I don't think a pull-up resistors going to help you out.

Can you explain what circuit your using this in, what protocols / components / supply voltage etc, it might help others better understand you question.

Hi Kevin,

I'd assumed, as had Edmund I would suspect, that you were original talking about some sort of DC signal, but looking at you last post, I am now thinking that maybe what you are talking about here is in fact an RF signal (otherwise why use SMA connectors).

If this is the case, this suggests that maybe what you are looking for is some way to change the DC offset of the signal, in which case a bias-T is a good choice, however, I still think you need to know more about what's going on here to make a recommendation. I'm still only picking out little clues here and there and making an educated guess at the end application.

As for other ways of doing it. who knows, could be a simple as a capacitor to block DC, without some clearer info on the signals, bandwidth, frequency etc, there isn't really enough to work on, but as a rough guide, any circuit that is employing SMA connectors is likely operating in the GHz range and will require a well matched Bias-T for DC signal injection.

I don't think a 741 will cut it, teasing out what info there is, it appears that what Kevin is talking about is adding a 1 volt DC bias to signal, and as he mentions SMA connectors, which are typically used in the GHz range, to a fairly high frequency signal (or at least a signal with high frequency components).

If I am interpreting correctly, he means turn this

In to this

At likely very high frequency (50ohm characteristic impedance).

The 741 has a gainbandwidth product of 1MHz

Am I missing something here? Can't you just use a pair of resistors in a potential divider to impose a +1V offset? Use a suitably high resistance so as not to impose a load on the source.

Depends on what you thinks going on here, Kevin didn't give a lot of info, but if you know what an SMA connector is, then you might take an educated guess that the -1V to 1V signal is probably some kind of 100s of MHz to GHz signal going to say an Antenna. If you think this is what might be going on, (and that's my guess, not a fact) then I don't think a switching regulator makes a lot of sense. I can't think of a single instance of ever seeing a switching regulator used in an R.F. signal path, it's not a natural place to find a DC to DC converter.

But this is all just guess work as to the end application and could be completely wrong, I was just trying to help Kevin out and based on some of the technologies he's mentioned my guess is this is a Radio Frequency signal path which for some reason needs a D.C. Bias applied to the signal, if that's the case, then I'd at least start by looking at a bias-T.

If memory serves, the below should be a basic circuit for a Bias-T