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In the circuit on the figure, a non-linearized VCR design, the voltage-controlled resistor, the LSK489C JFET, is used as a programmable voltage divider. The VGS supply sets the level of the output resistance of the JFET. The drain-to-source resistance of the JFET (R DS) and the drain resistor (R 1) form the voltage-divider network. The output ...
A current–voltage characteristic or I–V curve (current–voltage curve) is a relationship, typically represented as a chart or graph, between the electric current through a circuit, device, or material, and the corresponding voltage, or potential difference, across it.
where or Vtsat is the threshold voltage measured at a supply voltage (the high drain voltage), and or Vtlin is the threshold voltage measured at a very low drain voltage, typically 0.05 V or 0.1 V. is the supply voltage (the high drain voltage) and is the low drain voltage (for a linear part of device I-V characteristics). The minus in the ...
where and are contact and channel resistances, respectively, / is the channel length/width, is gate insulator capacitance (per unit of area), is carrier mobility, and and are gate-source and drain-source voltages. Therefore, the linear extrapolation of total resistance to the zero channel length provides the contact resistance.
Because resistance is proportional to length, shortening the channel decreases its resistance, causing an increase in current with increase in drain bias for a MOSFET operating in saturation. The effect is more pronounced the shorter the source-to-drain separation, the deeper the drain junction, and the thicker the oxide insulator.
Electric charge flows through a semiconducting channel between source and drain terminals. By applying a reverse bias voltage to a gate terminal, the channel is pinched, so that the electric current is impeded or switched off completely. A JFET is usually conducting when there is zero voltage between its gate and source terminals.
For a nearly ideal current source, the value of the resistor should be very large but this implies that, for a specified current, the voltage source must be very large (in the limit as the resistance and the voltage go to infinity, the current source will become ideal and the current will not depend at all on the voltage across the load).
CMOS ICs have generally borrowed the NMOS convention of V DD for positive and V SS for negative, even though both positive and negative supply rails connect to source terminals (the positive supply goes to PMOS sources, the negative supply to NMOS sources). In many single-supply digital and analog circuits the negative power supply is also ...