Invert channel with one switch

[cupoftea]

Hi,
We have a square wave oscillator....sometimes we want to pass through the signal itself, and sometimes we want to pass through the inverted signal. We want to change between the two with a single manual switch.
Can you think of any easier ways than the attached. I guess an analog changeover switch is good but they are often nil stocked....if i put one on the test pcb, its bound to go nil stocked.
Any other ways?

LTspice and pdf attached of the "bad" way

 

[FvM]

Use XOR gate.

 

[cupoftea]

thanks i tried xor, but to no avail, as attached (LTspice)

 

[betwixt]

Rather complicated - you could just use a TTL or CMOS XOR logic gate. Connect your signal to one input and switch the other between logic 0 and 1. The output will invert according to the logic level you apply. Only one gate is needed and no buffering is needed.

Brian.

 

[cupoftea]

thanks youre right, but xor needs 5 NAND minimum, and we only have 4 to play with

--- Updated Sep 2, 2021 ---

Even De Morgan's laws arent working today...this five nand xor doesnt work (LTspice)

xor-with-nand hosted at ImgBB

Image xor-with-nand in Cupoftea's images album

ibb.co

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--- Updated Sep 2, 2021 ---

oh right, LTspice doesnt "see" the GND symbol as a logic low input, even though its supposed to be 0V, and i declared the Ref as 1.5V.
So the xor does work after all. I should have believed De Morgan over LTspice

 

[danadakk]

thanks i tried xor, but to no avail, as attached (LTspice)

The control input is a sign changer, so should be a freq << signal input
in order to see the sign of output change.

Regards, Dana.

 

[mtwieg]

thanks youre right, but xor needs 5 NAND minimum, and we only have 4 to play with

What. If this is a homework assignment with arbitrary restrictions you should say so right off the bat.

 

[betwixt]

thanks youre right, but xor needs 5 NAND minimum, and we only have 4 to play with

I think I need new glasses.

Brian.

 

[crutschow]

Here's the XOR circuit using four 2-input NAND gates (it shows Schmidt-trigger NANDs but standard NAND gates can be used):
Note the change in output phase (red trace) relative to the input signal (green trace) when the phase control line (yellow trace) changes state.