How can I get a quartz crystal to make square waves at 4.096MHz? So far I have the 4.096MHz quartz crystal and this schematic I saw:
Where can you find an amplifier with a single input and what voltage should I use?
You can make a Pierce Oscillator similar to that shown in your question:
The "single input amplifier" is usually a simple CMOS inverting gate, like the 74HC7404 (6 inverters in one package), SN74HC14D (single inverter) or similar.
Note the series R mentioned above. The above came from this Fairchild App Note which goes into some detail on the design process.
You can only pull the frequency of a crystal oscillator a very small amount, so you will need a 4.096MHz crystal. Either that or you will need to use something else such as a PLL.
Generally Xtals below 30MHz are fundamental parallel mode resonance like LC expect Q is 3K and high impedance 180deg phase shift at resonance. THis means you need negative feedback using an inverter not a series mode with a non-inverter. Try both buffered x1000 gain and unbuffered x10 gain inverter CMOS chips and ensure spurious harmonic oscillator modes are avoided.The Xtal Q has enough gain with CMOS gain of 10x to get a square wave when feedback R is high Z.
Let Rf = 1~10 MΩ to self bias input to Vcc/2 let Rs = 10kΩ and C1 = 30~47pF or so. Let C2 = 100~1000pF in series with Varicap cathode while anode is to ground for reverse bias V vs cap control. Choose 0~12Vdc control range for varicap (or more) and select C1 to tune centre F.
I know this is a lot to take in a short paragraph so ask a Q? or read up on parallel VCXO's.
Here is a simple reference to appreciate Crystals more.
You can use an op amp in your circuit, ore use a 555 to generate square weaves
or do something like this: