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1

The notion of "resistance to which it discharges itself" is not very meaningful. It's better to think about the path of the current. When Vin goes to 1V, the left end of the MOSFET becomes the source and the \$V_{GS}\$ is a high voltage so the MOSFET becomes conducting. Current flows from the capacitor, through the MOSFET, and into the voltage source. In ...


2

In this circuit, collector-to-base capacitance would be close to \$C_{ob} \$. The base is almost grounded by C1 as far as radio frequency is concerned. \$ C_{ob} \$ is typically 2.5pf, maximum of 4pf when the DC collector-to-base voltage is 5V.(From a National Semiconductor data sheet). This measurement was done at 1MHz, not at 100MHz where this circuit is ...


1

I am not promoting the product but just to give you a hint. I have been using touch controllers and this is one smallest and just enough for the need. MBR3102 from Cypress It needs no extra pins. No software. It can be used to sense two touch buttons and is the cheapest in the family. If you can accomodate this in the design, give a try. I have also ...


0

You don't say which microcontroller but some manufacturers offer a software library for capacitive sensing. Essentially they perform measurement similar to Qtouch technology. Library or not, yes this should be possible, but if you do it yourself you are basically replicating patented technology.


0

With two pins you could create a software I2C interface and interface an IC (e.g. QTouch)


0

A few things to keep in mind: Ground is not special. Not in reality, and not in LTSpice. Ground is nothing more than the potential that we've decided to be 0V. It's a label, and one that is totally contrived and arbitrary. To drive my point home, it doesn't matter what part of your LTSpice circuit you pick as ground. If you move your ground from one ...


1

If you connect a fixed voltage at the input, current will flow through the capacitor and then through the resistor, with a resulting voltage drop across the resistor, which is also your output voltage. But the capacitor is charging, and as it does, it opposes the input voltage, so the current decreases. This shows up as a decreasing voltage across the ...


0

A differential is the mathematical expression for the rate of change. If the ramp rises with a constant slope rate the change will always be the same and therefore the output of a differentiator is a constant value when a ramp is present at the input.


36

It almost always denotes capacitance / voltage rating. Capacitance in µF, voltage in VDC. For example: 100/6.3 would be 100 µF, 6.3 VDC 22/10 would be 22 µF, 10 VDC


2

You don't need to run electricity through a wire to act as a stylus. Capacitive touch screens work by sensing changes in capacitance on a screen. Just plopping a coin on a screen won't register as a touch since that coin is an open circuit and can't modify the charge on that area of the screen. The charge on the screen is still the same. Conductivity alone ...


0

To see the effects change each value with the known worst-case tolerance then replace your 0V reference with a grounded impulse generator of say 1V on your ground to simulate broadband noise between ground. Use any rep rate to simulate 50 to 50MHz. CMRR is a function of your cable and circuit imbalanced impedance. Insert 0.5 uH/m between the generator to ...


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