Hello. I have questions for transmission line and please see the image below. This is the circuit what I made in which ZO and ZL are output and load impedances, respectively. The commercial voltage probe with oscilloscope is used to measure VL, voltage over ZL . VO, the voltage difference measured between output of the OP-AMP and ground by the probe is square signal of positive 13 V with ~ 10 μs pulse duration. Characteristic impedance of the transmission line ZC is 50 Ω. I have used this configuration with varying output and load impedances to test my knowledge of the transmission line theory. The followings are the results what I got. 1. ZL: 50 Ω, VL: 3.2 V of ~ 8.8 μs 2. ZL: 384 Ω, VL: 10.6 V of ~ 19.7 μs 3. ZL: 510 Ω, VL: 10.8 V of ~ 19.44 μs 4. ZL: 2376 Ω, VL: 12.6 V of ~ 17.89 μs All signals are quite clean square and the results doesn't matter whether ZO is 0 or 50 Ω. It seems the original pulse duration is only achieved when ZL and ZC are matched and amplitude of VL becomes closer to the original value as ZL rises. My original expectation was that clean signal of half amplitude should be seen when ZO and ZL are matched to ZC and for other cases I should be able to some ringing due to signal reflections. However, in measurement, about quarter of the original amplitude is observed at 1st case and for other cases I don't see any observable ringing and pulse duration is extended about twice. I'm even surprised to see signal transmission when ZO = 0 (reflection coefficient at boundary from source to transmission line is 1 as output impedance of the feedback loop OP-AMP is zero as far as I know) I really don't get how to explain my results and I would like to receive some comments. Thanks for reading and please give me some help.