RC all pass filters measuring problem, + solving negative impedance - Page 1
Forum section: electronics / beginners

author: lokajaudio
author_rank: Newbie
timestamp: May 03, 2021, 04:30:23 pm
content: .

author: lokajaudio
author_rank: Newbie
timestamp: May 05, 2021, 09:17:56 am
content: bump:)

author: The Electrician
author_rank: Frequent Contributor
timestamp: May 06, 2021, 05:32:55 pm
content: For your first problem, an obvious answer is: Get a better differential amplifier.A more practical answer might be this: Using a 4 channel oscilloscope with 10x probes, connect channel 1 to the left side of O1, and channel 2 to the right side of O1. Make sure that both channels are set to the same gain (volts per division) and that channel 1 is set to invert mode. Now what you see is the difference of the voltages across O1; in effect you are using the scope as a differential amplifier. Finally use channel 3 to display the voltage across I1 as your reference voltage.As to the second problem, it's not at all clear what you want to solve for. Do you want an input impedance, an output impedance, a transfer function? Will there be any impedances connected to the input or the output? Are you required to use any particular method to solve the network?Give much more detail.

author: lokajaudio
author_rank: Newbie
timestamp: May 14, 2021, 07:32:51 pm
content: Thanks for reply!problem 1 is solved, thanks!

author: The Electrician
author_rank: Frequent Contributor
timestamp: May 15, 2021, 12:03:23 am
content: I still don't understand what you are trying to do in part 2. I think you are using the word "solve" in a way that is not common on this board. Do you want to actually build some hardware that will have the response of an all pass, or do you want to find another circuit without negative resistances that will have your desired transfer function.

author: lokajaudio
author_rank: Newbie
timestamp: May 18, 2021, 08:56:37 pm
content: I just want to use some circuit after that one "with -Z impedances", which i think, has -Zoutright?, that will invert negative output impedance to positive, i found some structures that work as negative impedance converter, but i dont know if i can use them.Main problem is: to eliminate negative impedances in universal circuit

author: The Electrician
author_rank: Frequent Contributor
timestamp: May 18, 2021, 09:24:54 pm
content: What is your purpose? What will you use the circuit for? I might know of a better way, but I need to know what you want to accomplish.

author: lokajaudio
author_rank: Newbie
timestamp: May 19, 2021, 09:30:58 am
content: As i wrote, lattice LC all pass filter is based on that basic lattice circuit, which contain -Z. All i need, is to have pure circuit where output impedance will be +Z (get rid of those negative impedances, with some additional circuit at the output of basic lattice circuit)

author: The Electrician
author_rank: Frequent Contributor
timestamp: May 20, 2021, 04:10:00 pm
content: You didn't answer my questions in reply #6 so I have to guess what your purpose is.In problem 1 you have an RC all pass filter which has an output not sharing a common ground with the input. In essence it's equivalent to a lattice configuration. Perhaps you are wanting an all pass which is not a lattice configuration. There is an opamp circuit which can do the job at audio frequencies; maybe this will meet your needs:https://en.wikipedia.org/wiki/All-pass_filter