Tri-State Buffer

timswift

     Assuming you asked just a single transistor, the answer is no because a tri-state buffer needs two inputs: a control valve and x which is zero or one. The transistor base can switch the the emitter to collector  on or off only to control Hi-Z. But there is no buffer  to hold the state of zero or one! Read this to help What's a Tri-state Buffer? What to add is a buffer on the emitter before the transistor control gate for a tri-state buffer.

Clem

More read Digital Buffer and the Tri-state Buffer Tutorial

as clem57 has already said... basically no.

BUT

you can get close to it if your use does not require high drive currents, by treating hte transistor as an open collector drive and having a weak pullup on it you can get the situation where, when the transistor is off its collector will go high due to weak pullup but any other device on that line could control it (Pull it low or allow it to also stay high or even add to the high with its own weak pullup.)

This is how many systems share a connection to a device by using a common open collector drive. It is not quite the same as tri-state but comes pretty close.

If you ask yourself why you need tristate then the answer is usually to allow something else to control the connection, or at a minimum pretend your not connected to it. This is how I2C works, you can have upto 127 devices all on the same pair of wires, as there all open collector drive and there is a common pull up, the system still works and devices no participating in driving the piins are easily able to listen to the same pin, effectivly making it an input without more complex circuitry

I am planing to use it to connect the output of a SRAM to a data bus.

Tim

Then for sure you need a true tri-state buffer and possibly one with a built in latch, perhaps these may help  http://www.ti.com/lit/ds/snos333a/snos333a.pdf

Peter O, if I am interpreting him rightly, is referring to a totem-pole output with a passive pull-up.    Often called wire-or or wire-and.  This can act as another layer of logic, especially useful if the ultimate number of inputs is unknown.  Open collector devices are designed for this, but you can make a complementary/symmetry output like like OC with a diode.  You can do tricks like this with TS, sometimes you have to use diodes to protect from simultaneous events.  If you talk more about your intention, we can find the more appropriate method.

If you have OC but want pseudo-complementary/symmetry, you can use a current source for a top-load.

Thanks for the fast reply's.

A latch is not needed .  I am only connecting the value on the sram to the bus so the A register can read it. 

Tim