# How can I convert a high frequency sine signal to a square wave?

I'm trying to convert a high frequency sine wave signal (approximately 130 MHz) with lets say 3 Vpp into a square wave signal (also 130 MHz) with 0V and 5Vp. The square wave is subsequently used as a control signal to switch a MOSFET, which will be part of a switching amplifier I am developing.

I was thinking it might be possible with a Schmitt trigger, but I am not sure if this will work.

Does anyone have an idea or encountered a similar problem or can help?

Edit: Changed Switching amplifier to MOSFET

• Can you post a schematic? Oct 18, 2023 at 14:16
• I'm more concerned what you think you're going to switch at 130MHz? o_o Oct 18, 2023 at 14:52
• A Schmitt trigger is possible, but may or may not be called-for depending on where the sine is coming from, how noisy it is, and how much noise you need to eliminate from the signal. Such a trigger may cost more and/or be trickier to design for high speed than a simpler solution. You also may need to consider phase shift: how much can you tolerate? A trigger will introduce delay. Oct 18, 2023 at 15:24
• Is the input on a DC rail or is it 3Vpp about 0? Oct 18, 2023 at 15:26

I'm trying to convert a high frequency sine wave signal (approximately 130 MHz) with lets say 3 Vpp into a square wave signal (also 130 MHz) with 0V and 5Vp.

You can employ a straightforward approach using a high-speed comparator, such as the LTC6752, to convert a sine wave into a square wave. While this wave isn't perfect and may not be in phase, it's notably uncomplicated.

Your problem is going to be getting a nice square out of the other end.

Don't forget that a 'square' wave actually has finite rise and fall times.

Check with your switching amplifier specification what rise and fall times it can tolerate on its 'switching' input. You may find that you can simply amplify and shift your sine wave to swing between 0 and 5 V, and it will work.

If the edge rate is not quite fast enough from that, then an option nearly as straightforward is to amplify the sinewave a bit more, and clamp it to 0 V and 5 V.

If you need faster edges, then an excellent solution can be to use a 'universal' input clock buffer, these are usually CML. An LVDS receiver to logic output could also be pressed into service.