![]() On the other hand, if the device acts as a source of power, the load switching method is used. In general, if the device requires power to operate, the voltage sweep method is used. Using linear voltage sweeps and load switching, we will now look at the I-V curves of ideal components. Load switching techniques are used to measure the I-V characteristics of devices and circuits that supply power, such as voltage regulator circuits, solar cells, and batteries. This is because a resistor is governed by Ohm's law, and this is an ideal voltage source at a fixed voltage V S as the resistance value increases logarithmically, the current value decreases logarithmically. Note that in Figure 1.2(c), the (base 10) logarithmic value of current decreases linearly. The current that is supplied by the power supply is measured by an ammeter for each value of load resistance-shown in Figure 1.2(b)-and the voltage across the load is measured using a voltmeter-shown in Figure 1.2(c).įigure 1.2 (a) Schematic circuit for load switching I-V curve measurements shown here is an example of an ideal voltage source. The value of R L is varied over a large range and for each value of resistance the voltage (b) and current (c) are measured. Because devices can operate with small values of resistance (1-10Ω) as well as large values of resistance (10-1000kΩ), the resistors are varied logarithmically, i.e., from 10 to 100 to 1000 and so on. Typically, a resistor is used as the load to measure the power delivered by a current or a voltage source because they are linear devices that do not exhibit properties of hysteresis, i.e., the operation of the resistor does not depend on its previous state. The load is the device that electrical power is being delivered to, where power is defined as $$P = V \times I$$. Load switching is a method that involves measuring the current supplied by the power source for varying load resistance. For these devices, I-V curves are obtained by load switching. If you have a device that supplies voltage or current, such as a battery or a solar panel or a regular power supply, you cannot change the voltage across the device, because there is a specific voltage or current being generated by the device. The notion of time is relevant for components that respond to a change in voltage (such as a capacitor) rather than the instantaneous voltage (as with a resistor).įigure 1.1 (a): A linear sweep of voltage (V) with respect to time (t) (b): the corresponding voltage sweep in the current (I) - voltage (V) curve. It is important to understand that the V vs t information is implicitly present in the I vs V curve. Because it is impossible to physically sweep through all the voltages in an instant, it is important to understand that these measurements are made with respect to time as well.įigure 1.1 illustrates the translation of voltage sweep with respect to time ( V vs t) onto the X-axis of the current-voltage graph ( I vs V). Voltage sweeps involve the linear variation of the voltage, to obtain the corresponding measured output current. ![]() For devices that do not supply power, I-V curves are obtained by using linear voltage sweeps. The current-voltage ( I-V) relationship for a device is a current measured for a given voltage. We'll begin by looking at how to obtain an I-V curve for any component. More specifically, many non-linear devices such as diodes and transistors are used in operating regions in which they behave like ideal components-such as current sources, voltage regulators, and resistors.Īn understanding of I-V curves often provides insight into knowing how the device operates and helps us know how to operate a device in a way that enables the required functionality. The current (I) - voltage (V) relationship of electrical components can often provide insight into how electronic devices are used. This article discusses I-V curves for passive components, voltage sources, and current sources. ![]()
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