Control Signal Logic Levels

[lins13]

Hi Guys,
I have a signal which I must use as a control signal for a DAC. However the device the control signal comes from holds the signal at -3.3V for a low and +3.3V for a high. This cannot be changed. I need the signal to sit at 3.3V high normally and pulse to 0v for a low.

Essentially I have a signal that sits at -3.3V usually and pulses to +3.3V and I want this to sit at +3.3V and pulse low to 0V

I will need an inversion, i.e. some kind of NOT gate, but I am unsure what device can be used to change the signal levels

Any suggestions?

Thanks

 

[GUMY]

Just clamp the -3,3V signal to GND with Schottkey diode and resistor and then use any CMOS invertor gate.

 

[lins13]

if I do this, will it not make the high equal to 6.6V in addition as it is one track for both signals? That would be a problem

 

[GUMY]

No. You will just clamp negative voltage to GND. It will not affect positive voltage. Put resistor in series and diode (anode) to GND.

 

[lins13]

Thanks for the idea but I am going to use a comparator. I have very little drive current available and this lets me change the voltage levels and invert in one device.

 

[Tunelabguy]

You can use a comparator, but with a voltage swing of 6.6 volts, you could also use a single enhancement mode N-channel FET and the resistors to achieve the same thing.