I’m using a 555 timer in conjunction with a simple NAND & AND gate pulse generator to create a short 60 ns pulse that I use to set a four bit register made from JK flip-flops. I can see the short pulse on my scope. I thought I’d build a comparator circuit configured as a Schmitt Trigger to make a nice square wave from the pulse. I’m using a single comparator on a LM393N IC.
I’m pretty sure I have the resistors set up correctly to trigger the pulse on 1.0 V and 1.5V. This should produce ~50 ns square wave. I’ve verified the reference voltages on my breadboard for saturation and cut-ff and these look good.
I’m unable to produce a square wave from the short pulse. I checked the data sheet for timing information, but I didn’t see anything helpful. Does anyone know if the LM393 is capable of detecting a signal with pulse width around 60 ns? I suspect the limit might be 100 ns for f = 10 MHz (just a guess).
And yes, I do have a pull-up resistor on the transistor’s collector.
The LM393 is an old design, and way too slow to do what you want. The data sheet I have doesn’t give an output slew rate, but the “large signal response time” to a single input transition is given as 300 ns.
And the 300ns rating is the best that part can do with ideal input conditions.
Take a look at various high speed CMOS logic gates which may be capable of what you are looking to do. Look for parts using VHC or better technology to ensure the lowest propagation delays. One of the first parts I found is the 74VHC00 quad 2-input NAND gate. They have propagation delays in the area of 11.5ns worst case but they do not fully describe what the output characteristics are. They can drive a relatively high current so if you minimize the capacitance connected to its output, your rise times will be faster. I’ve never had the need for hard edges at the speed you require so I don’t have an immediate recommendation for you. It may require some experimentation on your part unless someone has some directly related experience that they care to share.