Note: Corrected logic inversion problem.
2nd Update: Fixed output voltage range, using MOSFET rather than BJT
The basics of the problem as you have described it, appear to be called either a "logic level shifter" or converter. The essence is that you have a digital logic (binary) signal at a given signal level, and you wish to use adapt it to another signal level.
Digital logic signals are normally classified according to the original logic family they belong to. Examples include TTL (low: 0, high: +5V), CMOS (low: 0, high: 5 to 15V), ECL (low: -1.6, high: -0.75) , LowV (low: 0V, high: +3.3).
Ideally, you should also be aware of the switching threshold as well. E.g Logic signal voltage levels that shows the TTL logic voltage levels in the first two graphics.
If you wish to amplify a logic signal that is either 0 or 1.4V, then a single transistor can be configured as an electronic switch to act as a level converter.
(src: mctylr )
In your application the output is the 5V-level output (0 or 5V depending on low/high status) and
M1 could be a common small-signal N-channel enhancement mode MOSFET transistor, the 2N7000 in TO-92 plastic through-hole, and SMT packaging.
R2 should be 330Kohms, (additional resistor component details are not critical, e.g. 1 or 5% tolerance, 1/8 to 1/4 Watts rating are fine).
The resistor's resistance values is not particularly critical, I picked an approximate standard value so that if
M1 is not conducting then the output will be below ~0.8 V, while when
M1 is conducting (i.e. the input is 1.4V, 'high') then the output will be approximately 5V. I picked the value using a quick SPICE simulation.
V3 is a +1.4V voltage source, and
V2 is a +5V voltage source.
The other values (tolerance and wattage) are common through-hole component values used to select real-world component, but are not critical in this application.
That's a very simple and small circuit, costing about twenty-five cents or less for three common electronic parts.
Since you didn't mention any high-speed requirements (i.e. switching speed), so this should work in most simple cases.
I've adopted this approach of using a MOSFET rather than a bipolar junction transistor
as I had trouble making a single BJT give the desired voltage swing when switching. From a design point of view, the nice thing about FETs (and MOSFETs) is that they are voltage controlled devices (in terms of a design model), rather than current-controlled as BJT are.