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Author Topic: Resistance Scaling with Voltage  (Read 5527 times)

Offline jadaro2600

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Resistance Scaling with Voltage
« on: June 15, 2010, 04:17:40 AM »
I'm working on some schematics for an in-line component that will scale resistance with voltage... the lower the voltage, the lower the resistance.

There are some obvious components which match up for the job:
MOSFET
JFET
VCR ( voltage controlled resistor )

But these have some statistical issues which I'm wary of, namely the threshold voltage.  The source voltage would be low, near the ( ohmic ) region of MOSFETs or JFET.  Ideally there would be negligible current flowing through gate to drain region.

BJT's are out of the question for this, there's runaway and a voltage drop from Base to Emitter.

I think what I need is depletion mode MOSFET, small signal characteristics.

This post was made in this section because of it's obvious ability to be added to a JTC with the advantages of thwarting the effects of resistance at the base of a transistor causing a premature halt to the functionality of a circuit.

I want to turn the JTC into a circuit capable of exceeding the rated mAh capacity of common alkaline batteries.  Usually tested down to 1.0 or 0.9 volts from a nominal 1.5 volts, the batteries could exhibit a mAh capacity twice that as they are rated, if not three times.

The idea is to take a one-time use battery and substantiate the usefulness of the circuit down to approximately the threshold of germanium transistors ( battery source of 0.32 volts, or there abouts ) ...  This would mean powering the JTC with a nominal current ( ~20mA ) on a 1.5 volt battery, down to 0.3 volts.

Furthermore, with the capability of scaling resistance, the source voltage could be increased without changing the schematic components ( minimal tweaking, no change of components if done correctly ).  This would allow someone to draw two batteries down to 0.3 volts, or 0.15 volts each ( even more energy extracted ).

This would be a deep discharge, not recommended for rechargeable batteries, only one time use batteries.  Essentially, someone could take two 'dead' batteries from normal use and place them in the circuit to draw the remaining usefulness out of them.

- - - - -

I don't currently have any depletion mode MOSFETs, so I can't test any specifically.

Offline jadaro2600

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Re: Resistance Scaling with Voltage
« Reply #1 on: June 15, 2010, 04:36:41 AM »
Here is a simple concept diagram.

Any input would be appreciated.