I have a harebrained idea on how to make a 200Mhz Frequency Counter using an AVR. The basic concept is to use a 74VHC4040 counter that is rated for 200Mhz and the AVR just as the UI / counter reader. The reference is a 1 PPS input signal. Zero the counter. Start the counter using the 1 PPS into a T flip-flop. When the flip-flop goes high, an AND gate feeds the input signal to be counted to the 4040 and the AVR counts the overflows from q12 for the 4096s bit on the INT0 line. When the next PPS signal comes in the T flip-flop goes low, the signal is disconnected from the 4040, the AVR reads the rest of the bits, and lastly resets the counter for the next go-through. So you get one count every 2 seconds. Real basic stuff. The problem is that the PPS signal is 0.5V and the input signal may not be of a TTL triggering strength either. Is this a job for an opamp to boost these incoming signals? What would be the right one to try? I would assume that 200Mhz is not a speed that that most opamps do not operate at. Or is this more of a job for a high speed comparator?
P.S. I haven't sampled a part from Linear in a while. Suggest Linear parts and I will test them out for you and report the results here. 8)