Hello.
I have questions for transmission line and please see the image below.
This is the circuit what I made in which Z_O and Z_L are output and load impedances, respectively. The commercial voltage probe is used to measure voltage over Z_L with oscilloscope. V_O, 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 Z_C 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. (V_L is measured voltage over the load)
1. Z_L: 50 Ω, V_L: 3.2 V of ~ 8.8 μs
2. Z_L: 384 Ω, V_L: 10.6 V of ~ 19.7 μs
3. Z_L: 510 Ω, V_L: 10.8 V of ~ 19.44 μs
4. Z_L: 2376 Ω, V_L: 12.6 V of ~ 17.89 μs
All signals are quite clean square and the results doesn't matter whether Z_O is 0 or 50 Ω.
It seems the original pulse duration is only achieved when Z_L and Z_C are matched and amplitude of V_L becomes closer to the original value as Z_L rises.
My original expectation before doing this test is that clean signal of half amplitude is seen when Z_O and Z_L are matched to Z_C 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 the pulse duration is extended about twice. I'm even surprised to see signal transmission when Z[SUB]O[/SUB] = 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 these results and I would like to receive some comments.
Thanks for reading and please give me some help.
Mod edit:
Please refer to another same topic was closed --
Why does my non-inverting feedback Op Amp have loading effect?
I have questions for transmission line and please see the image below.
This is the circuit what I made in which Z_O and Z_L are output and load impedances, respectively. The commercial voltage probe is used to measure voltage over Z_L with oscilloscope. V_O, 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 Z_C 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. (V_L is measured voltage over the load)
1. Z_L: 50 Ω, V_L: 3.2 V of ~ 8.8 μs
2. Z_L: 384 Ω, V_L: 10.6 V of ~ 19.7 μs
3. Z_L: 510 Ω, V_L: 10.8 V of ~ 19.44 μs
4. Z_L: 2376 Ω, V_L: 12.6 V of ~ 17.89 μs
All signals are quite clean square and the results doesn't matter whether Z_O is 0 or 50 Ω.
It seems the original pulse duration is only achieved when Z_L and Z_C are matched and amplitude of V_L becomes closer to the original value as Z_L rises.
My original expectation before doing this test is that clean signal of half amplitude is seen when Z_O and Z_L are matched to Z_C 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 the pulse duration is extended about twice. I'm even surprised to see signal transmission when Z[SUB]O[/SUB] = 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 these results and I would like to receive some comments.
Thanks for reading and please give me some help.
Mod edit:
Please refer to another same topic was closed --
Why does my non-inverting feedback Op Amp have loading effect?
Last edited: