S
Spehro Pefhany
- Jan 1, 1970
- 0
John Larkin said:[...]John Devereux wrote:
John Devereux wrote:
[...]Here's a minus one ohm resistor:
. 1 ohm
. ___
. .---|___|-.
. | |
. -1 ohm --> | |\| |
. o--------o--|-\ |
. | >---|
. .--|+/ |
. | |/| |
. | ___ |
. o---|___|-'
. | 1 ohm
. .-.
. | |1 ohm
. | |
. '-'
. |
. ===
. GND
It's incomplete. It has no power supply.
Hi Silvia,
You can use a battery.
Which is significant. You cannot simulate a negative resistance
without a power supply, because it is an energy source.
Of course, the energy comes from the supply.
The fact that it needs a power supply emphasises the fact that it
only simulates a component with negative resistance. It isn't a real
negative resistor. The highly desirable real negative resistor, were
one to exist, would function indefinitely. A simulation can only
function as long its energy reservoir lasts.
But it is nevertheless a negative resistor / resistance during that
time IMO. Put it in a box with a bettery and bring out the input
terminal and GND. It's a negative resistor - i.e. a two terminal
circuit with negative resistance. It will have limits of operation
determined by the components used (but so does a "real" one).
That's the circuit I used, in a box with two 9-volt batteries, in my
class project ca 1968. I used a 709 opamp, as I recall. It was fun,
plugging negative numbers into all the classic circuit equations and
seeing the actual waveforms.
Sylvia should try it.
There's (at least) one nice direct application of this idea -
compensating for the winding resistance in a DC motor speed
controller.
<http://focus.tij.co.jp/jp/lit/an/sboa043/sboa043.pdf>
This is SOP in brush DC motor drives. It is called "IR Compensation"
in the industry.