Resistors will be needed in all cases when driving LEDs from a voltage source, unless you are using LEDs that already have a built in current limiting IC inside the package (a few do these days, for example I have some blinking LEDs that need no resistor they have a blinker IC built in that also limits current).However you have another problem that you obviously are not aware of. 8 LEDs rated at 1.5V in series totals exactly 12V. But your battery is only rated at 12V. As the battery discharges its voltage slowly drops, the moment it drops under 12V all the LEDs will turn off! I strongly recommend that you use no more than 7 LEDs rated at 1.5V in a circuit powered by a 12V battery, so that the battery can actually gets a chance to discharge beyond its knee voltage. In this case the resistor will drop the remaining voltage, whatever it is depending on the charge state of your battery.
The forward voltage at which the current through the junction starts increasing rapidly, is called the knee voltage or cut-in voltage.
0.63 is the knee voltage & 0.37 is the cutoff voltage
Knee voltage, also known as threshold voltage, in Gallium Arsenide (GaAs) refers to the minimum voltage required to initiate significant current flow in a GaAs device, such as a transistor or diode. This voltage is crucial for determining the operational characteristics of GaAs-based electronic components. Typically, knee voltage in GaAs devices is lower compared to silicon counterparts, making GaAs favorable for high-frequency and high-efficiency applications.
A: Perfect example is a zener. As input voltage increases the current at the knee increases almost linearly at the zener voltage. If the inputs varies up or down then the current will vary up or down at the preset voltage making a zener a voltage regulator because of this feature
The knee voltage for silicon is approximately 0.7V, while for germanium it is around 0.3V. The knee voltage is the voltage at which a diode starts conducting significantly.
Resistors will be needed in all cases when driving LEDs from a voltage source, unless you are using LEDs that already have a built in current limiting IC inside the package (a few do these days, for example I have some blinking LEDs that need no resistor they have a blinker IC built in that also limits current).However you have another problem that you obviously are not aware of. 8 LEDs rated at 1.5V in series totals exactly 12V. But your battery is only rated at 12V. As the battery discharges its voltage slowly drops, the moment it drops under 12V all the LEDs will turn off! I strongly recommend that you use no more than 7 LEDs rated at 1.5V in a circuit powered by a 12V battery, so that the battery can actually gets a chance to discharge beyond its knee voltage. In this case the resistor will drop the remaining voltage, whatever it is depending on the charge state of your battery.
Knee voltage (cut in voltage) :-The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage Breakdown voltage :-It is the minimum reverse voltage at which the P-N Junction can conduct without damage to the current
Cut in voltage (Knee voltage): The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage.
The knee point voltage of a CT is the voltage at the "knee" of a I-V characteristic (if you increase voltage, and plot this voltage with respect to the current flow, you will see a logorithmic type response). The knee is usually specified as 10% distortion (ie, the voltage is 10% less than you would expect relative to the current flow). beyond the knee point, the CT is considered in saturation. This applies to amplifiers / transistors as well as CTs. Transistors used as ampifiers are operated in the "linear region", or the region below the knee point of that particular transistors I-V characteristic.
The forward voltage at which the current through the junction starts increasing rapidly, is called the knee voltage or cut-in voltage.
It is about 0.7 volt for Silicon diodes.
0.63 is the knee voltage & 0.37 is the cutoff voltage
Knee voltage, also known as threshold voltage, in Gallium Arsenide (GaAs) refers to the minimum voltage required to initiate significant current flow in a GaAs device, such as a transistor or diode. This voltage is crucial for determining the operational characteristics of GaAs-based electronic components. Typically, knee voltage in GaAs devices is lower compared to silicon counterparts, making GaAs favorable for high-frequency and high-efficiency applications.
A: Perfect example is a zener. As input voltage increases the current at the knee increases almost linearly at the zener voltage. If the inputs varies up or down then the current will vary up or down at the preset voltage making a zener a voltage regulator because of this feature
the voltage at which electronic device operates is callled threshold voltageand the voltage at which device show cinduction in forward biased stste
10 % increase in voltage gives you 50 % increase in excitation current is called knee point voltage. To measure this first demagnetise the CT and apply voltage gradually from secondary keeping primary winding open circuited. while doing this above phenomeneo will be obsesrved.