output in logic gates

[jovabiot]

How can i have +1 and -1 as logic states with common gates instead of 5, 0 volt?? Can i have it with external transistors? I am working with a digital signal of 50 mhz and an logic F, ALS, ACT... thanks

 

[ljcox]

How can i have +1 and -1 as logic states with common gates instead of 5, 0 volt?? Can i have it with external transistors? I am working with a digital signal of 50 mhz and an logic F, ALS, ACT... thanks

Do you mean +1 and -1 Volt? If so, you can't do it since the ICs need at least a 3 Volt supply (I have not checked the F, ALS, ACT types, they may need 5 Volt).

You could use a 5 Volt supply and a transistor to do the level shifting.

Alternatively, you could use say +2.5 and -2.5 Volt supplies (assuming the ICs need 5 Volt) and a resistor divider to obtain +1 and -1 Volt.

Len

 

[jovabiot]

transistor for shift

witch circuit can i implement for doing the voltage shifting for obtain +1 and -1 volt insted of +5 , 0 volt? a transistor and a voltage supplie , but how? THANKS

 

[ljcox]

Second edit.
After further thought, I think all you need is a capacitor to block the DC and 2 resistors connected as an attenuator & possibly another capacitor to compensate. But in order to design such a device, we would need to know the output impedance of the driver and the input impedance of the other device.

Len

 

[Russlk]

50 mHz is too fast for ALS or ACT, 74F will even be marginal. You may find units that work, but you cannot rely on it. ECL should work, or some of the newer 3 volt logic. Why do you want +1 and -1, why not +1.5 and -1.5?

 

[jovabiot]

logic levels

i need +1 and -1 volt fot doing a bpsk modulation, but i think that +1.5 and -1.5 is also good values for it. How obtain it keeping the properties of fanout of the gates? witch circuit with transistors can i use? ( 50 Mhz) finally i have thougth to do this with operational amplifiers as a comparator. Do you know if it is possible at this frequency? thanks

 

[Russlk]

I did not find an IC that would do 50 mHz, but this circuit should work: