Add two signals without op-amp

"Daku the Diabolical "

Fuckhead.

... Phil

Low Z sources, "add", but net "gain" is 1/2:

Source_1 o----\/\/\/\/\-----o | | o----- OUTPUT | | Source_2 o----\/\/\/\/\-----o

(R's are equal.) ...Jim Thompson

Question is too broad.

Mini-circuits makes a broad band power splitter/ combinder. ZSC-2-2 is in my RF drawer. 2kHz to 60 MHz. Inside are a couple of torroidal transfomers (at right angles),two caps?? and a resistor. I tried to reverse engineer the circit once, but never figured out how it works.

George H.

Passive mixer example at bottom of this page

The problem is ill-defined. Details?

And what do you mean by "adds phase"?

John

As far as I remember, an inverting op-amp based summing amplifier adds 180 degree phase. I am trying to add a square wave signal, with a large DC +ve offset, to a plain -ve DC offset, to neutralize the former, and get the square wave out. I have in the past tried a capacitive divider, AC coupling, but the DC offset does not go away, even when I have a big value resistor to ground at the AC coupling capacitor, to drain the DC.

I have tried this already -- not very helpful. If you see my new post, I explain the reason why I am doing this.

Hi Daku,

Well, this is easy to do. Convert your signals to current (as far the signal is not given as current) and solder them together to one point. As far as Kirchhoff says the current in the third wire that you soldered to this point is the summ of the former two.

Where was the problem?

Marte

If that's all it is, use a comparator. Trivial- something for the basics ng.

For what value of large 10V with 1mV signal or 10kV with 1V signal?

If that is all that is bothering you about the opamp then add a unity gain inverting buffer afterwards.

The circuit Jim suggested should do it iff you have specified the problem correctly. You do realise it would probably be a lot easier to take the difference of signal on +ve DC plateau and a +ve reference.

Start again by describing what it is you are trying to measure.

Regards, Martin Brown

One would certainly hope so. But maybe it really subtracts 180 degrees phase? :-)

You can do this with AC coupling and an appropriate bias, but what you probably really want is a "DC restorer." Google it, or see the first hit here:

---Joel

Hi Joel,

NEver. There is really no phase shift, neither 180° nor -180°. It is simply an inversion.

May be the BB-Appnote sboa003.pdf from

Marte

Ah, but if I give you a black box and you can only measure the input and output terminal responses (and you're not allowed to interrupt the input), how would you know? :-)

Does a half-inverter logic IC provide a 90 degree phase shift over a range of frequencies? :-)

Hi Joel,

Just right at the beginning of the signal. There is really no shift, just inversion. This is quite often a big difference but not in case of a strict stationary signal. But tell me the sense of such a signal that never starts and never ends...

Very impressive logic component I never used before ;-)

Marte

So use a non-inverting opamp stage.

NT

create a voltage comparator using a comparator chip, many out there. input your external DC offset into the (+) input of this circuit, input a Reference voltage that matches your offset that you are trying to remove into the (-) input of the comparator, with a small increase over that threshold to adjust where you want the square wave to be recognized.

Basically, until your external square wave signal exceeds the reference, the output will remain in the off state with no offset.

This simple circuit will not phase shift your signal 180.

You can use a NPN emitter circuit with a threshold bias at that emitter and have it bias a high side PNP on the collector side to pulse the output on when the input at the NPN base exceeds 0.7 volts higher than the emitter.

I guess it's up to you.

If you would like an ASCII print I guess I could give AACircuit a try..

Jamie

Only if they are coming from a zero source impedance..

"HardySpicer" "Phil Allison" "Daku the Diabolical "

Only if they are coming from a zero source impedance..

On wot planet ??

.... Phil