Talk:Logarithmic resistor ladder

Exact manner that circuit is reversed

I found an example of a logarithmic resistor ladder circuit published in a 2002 Russian magazine RadioHobby by the creator: https://www.diyaudio.com/community/threads/constant-impedance-relay-resistor-logarithmic-attenuator.21198/#post-246385

I was curious enough to simulate it circuit in circuitjs (simulation netlist at bottom of this comment). In the top circuit I have a 10V voltage source on the left going into a 10k resistor going into the ladder *from left-to-right* which is terminated by a 10k resistor load on the right.

In this wiki's "Circuit Variations" section it currently says:

• The circuit as depicted above, can also be applied in reverse direction. That correspondingly reverses the role of constant-input and constant-output resistance equations.

So in my simulation the bottom half circuit has the voltage input on the right going into a 10k resistor going into the ladder *from right-to-left* terminated by a 10k resistor load on the left.

And whatever binary number I set the switches to, for both cases the output voltages match. So I think I did it right. But I want to be very clear in the wiki's wording about *in what manner* the circuit "can also be applied in reverse direction". It is written a little vague. Cause I had to swap around the source resistor and terminating resistor. By swapping the sources and termination, it is as if the individual stages themselves get mirrored, but their ordering does. It is a little hard to explain with the circuit included in the Wikipedia article. The RadioHobby article though has terminal nodes on the input and output and doesn't actually connect the input (just says "INPUT 10k") and the output has a terminal dot and break in the wire before it shows the terminating load resistor. So I'm wondering maybe the wiki's circuit could be more easily explained if Rsource and Rload were simply not included. And then maybe later when explaining how to reverse directions can maybe show these two reversed configurations like in my circuitjs simulation. But I don't know how best to explain it and am new to the topic of logarithmic ladders.

circuitjs simulation:

$ 1 0.0000049999999999999996 10.20027730826997 50 5 43 5e-11 r 416 -64 480 -64 0 9750 S 480 -16 416 -16 0 1 false 0 2 w 416 -64 416 -32 0 w 480 -64 480 -16 0 r 416 0 416 112 0 258 w 416 112 496 112 0 w 480 -64 496 -64 0 r 496 0 496 112 0 6.31 w 560 -64 560 -16 0 w 496 -64 496 -32 0 S 560 -16 496 -16 0 0 false 0 2 r 496 -64 560 -64 0 10000 w 496 112 592 112 0 w 560 -64 592 -64 0 r 592 -64 592 112 0 10000 w 592 -64 640 -64 0 p 640 -64 640 112 1 0 0 w 592 112 640 112 0 w 400 -64 416 -64 0 w 336 112 416 112 0 r 336 0 336 112 0 1880 w 400 -64 400 -16 0 w 336 -64 336 -32 0 S 400 -16 336 -16 0 1 false 0 2 r 336 -64 400 -64 0 8410 w 320 -64 336 -64 0 w 256 112 336 112 0 r 256 0 256 112 0 6610 w 320 -64 320 -16 0 w 256 -64 256 -32 0 S 320 -16 256 -16 0 1 false 0 2 r 256 -64 320 -64 0 6020 w 240 -64 256 -64 0 w 176 112 256 112 0 r 176 0 176 112 0 17100 w 240 -64 240 -16 0 w 176 -64 176 -32 0 S 240 -16 176 -16 0 1 false 0 2 r 176 -64 240 -64 0 3690 w 160 -64 176 -64 0 w 96 112 176 112 0 r 96 0 96 112 0 38600 w 160 -64 160 -16 0 w 96 -64 96 -32 0 S 160 -16 96 -16 0 1 false 0 2 r 96 -64 160 -64 0 2060 w 80 -64 96 -64 0 w 16 112 96 112 0 r 16 0 16 112 0 81900 w 80 -64 80 -16 0 w 16 -64 16 -32 0 S 80 -16 16 -16 0 1 false 0 2 r 16 -64 80 -64 0 1090 r -96 -64 -32 -64 0 10000 w -32 -64 16 -64 0 w -32 448 16 448 0 w -32 272 16 272 0 r -32 448 -32 272 0 10000 r 16 272 80 272 0 1090 S 80 320 16 320 0 1 false 0 2 w 16 272 16 304 0 w 80 272 80 320 0 r 16 336 16 448 0 81900 w 16 448 96 448 0 w 80 272 96 272 0 r 96 272 160 272 0 2060 S 160 320 96 320 0 1 false 0 2 w 96 272 96 304 0 w 160 272 160 320 0 r 96 336 96 448 0 38600 w 96 448 176 448 0 w 160 272 176 272 0 r 176 272 240 272 0 3690 S 240 320 176 320 0 1 false 0 2 w 176 272 176 304 0 w 240 272 240 320 0 r 176 336 176 448 0 17100 w 176 448 256 448 0 w 240 272 256 272 0 r 256 272 320 272 0 6020 S 320 320 256 320 0 1 false 0 2 w 256 272 256 304 0 w 320 272 320 320 0 r 256 336 256 448 0 6610 w 256 448 336 448 0 w 320 272 336 272 0 r 336 272 400 272 0 8410 S 400 320 336 320 0 1 false 0 2 w 336 272 336 304 0 w 400 272 400 320 0 r 336 336 336 448 0 1880 w 336 448 416 448 0 w 400 272 416 272 0 p -96 272 -96 448 1 0 0 r 592 272 656 272 0 10000 w 560 272 592 272 0 r 496 272 560 272 0 10000 S 560 320 496 320 0 0 false 0 2 w 496 272 496 304 0 w 560 272 560 320 0 r 496 336 496 448 0 6.31 w 480 272 496 272 0 w 416 448 496 448 0 r 416 336 416 448 0 258 w 480 272 480 320 0 w 416 272 416 304 0 S 480 320 416 320 0 1 false 0 2 r 416 272 480 272 0 9750 w -96 448 -32 448 0 w -96 272 -32 272 0 R -96 -64 -144 -64 0 0 40 10 0 0 0.5 R 656 272 704 272 0 0 40 10 0 0 0.5 w 256 112 256 128 0 g 256 128 256 144 0 0 w 256 448 256 464 0 g 256 464 256 480 0 0 x -161 -78 -127 -75 4 24 Vin x 695 262 729 265 4 24 Vin x 710 32 758 35 4 24 Vout x -164 366 -116 369 4 24 Vout

Em3rgent0rdr (talk) 02:05, 28 June 2023 (UTC)