Re: How to measure two signals with a delay of less than 1 n
It may be a building block (or the heart) of time-to-digital. Circuits can be found in literature, particular about nuclear physics instrumentation, I don't have a reference at hand. I've seen the circuit also in industrial instrumentation as US doppler flow measurement.
Some variants exist. Generally, you have a capacitor, and a switched current source, e. g. a differential pair. The current source is switched to load the capacitor for the intervall between the two pulse edges. The voltage at the capacitor is sampled then and processed, e. g. to a digital value.
The most critical design part typically isn't the time-to-voltage conversion but to generate a precise trigger from real-world signals. Special circuist as constant fraction triggers haven been designed for this purpose.