Choosing the right device & circuit to convert DC to AC?

Welcome to EP.

What you need is called a "power Inverter".

But your requirements are not defined properly.
1.What are you going to power with it? at what voltage?
2.There is a great difference between square and sine wave ,what should it be?
3.Define clean and stable in numerical quantities.

 

Yeah, @dorke is on the right track with his questions. Let's cut to the chase: tell us what you are trying to DO and we will offer advice and/or suggestions on HOW to do it. Maybe something like this:

So, I found this really neat thermopile that produces at least 10 W of DC power when I place it on top of my gas grill and turn the heat way up. It's pretty low voltage though, only about 3 V when I place a one ohm resistor across the output. I wanna use this as a power source for a variable-frequency piezoelectric transducer that I hope will annoy mosquitoes and keep 'em away from my next barbecue cook-out. Pleez help quik cuz summer is fading fast!

 

74LVC14A
Here is your square wave signal with variable R in series with fixed R to give f range required using datasheet for a suitable C value.

You will need high side and low side MOSFET switches to transfer DC power into AC power..

10W at a few volts needs a few amps with a 1Ω load e.g. 3.3V * 3.3A with DC
with AC and load connected to + or - we only transfer have the power so you can choose 0.5Ω load for 6.7A or use a "half-bridges" with dual complmentary gate drivers. If the load is 500mΩ then you will want the driver switch to be <5% of load for efficiency or < 25mΩ

This is just one way

 

Voltage to frequency converter chip?