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How the threshold voltage changes the transfer curve for a comparator?
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∙ 12y ago
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Why is a Schmitt trigger called a regenerative comparator?
A Schmitt Trigger is a comparator, because it compares its input voltage to a "threshold" voltage, but it has _two_ threshold voltages (the upper and lower trigger voltages), and which threshold voltage is used depends on the output state. If the input voltage is higher than the upper trigger voltage, the output will be high (for a non-inverting Schmitt trigger). In this state, the input is compared to the lower threshold voltage, so the input now has to go below the lower threshold voltage before the output will go low. The threshold voltage depends on the output state, such that a high output selects the lower threshold voltage, and a low output selects the upper threshold voltage. This can be visualised as using a fixed threshold but adding a small voltage (the difference between the upper and lower threshold voltages, also called the hysteresis voltage) to the input voltage before it is compared. This small added voltage is high when the output is high, and low when the output is low. A small amount of the output voltage is effectively being added to the input voltage before it is compared to a fixed threshold. This is positive feedback, also called regenerative feedback. So a Schmitt trigger operates as a voltage comparator, and a small amount of the output is added to the input, so it uses positive or regenerative feedback.
What is a threshold voltage in scr?
the voltage at which the current conduction occur
What is the voltage threshold for GAAs?
1.7 volts
Working process of 555 timer?
Comparator 1 has a threshold input (pin 6) and a control input (pin 5). In most applications, the control input is not used, so that the control voltage equals +2/3 VCC. Output of this comparator is applied to set (S) input of the flip-flop. Whenever the threshold voltage exceeds the control voltage, comparator 1 will set the flip-flop and its output is high. Ahigh output from the flip-flop saturates the discharge transistor and discharge the capacitor connected externally to pin 7. The complementary signal out of the flip-flop goes to pin 3, the output. The output available at pin 3 is low. These conditions will prevail until comparator 2 triggers the flip-flop. Even if the voltage at the threshold input falls below 2/3 VCC,that is comparator 1 cannot cause the flip-flop to change again. It means that the comparator 1 can only force the flip-flop's output high.To change the output of flip-flop to low, the voltage at the trigger input must fall below + 1/3 Vcc. When this occurs, comparator 2 triggers the flip-flop, forcing its output low. The low output from the flip-flop turns the discharge transistor off and forces the power amplifier to output a high. These conditions will continue independent of the voltage on the trigger input. Comparator 2 can only cause the flip-flop to output low.From the above discussion it is concluded that for the having low output from the timer 555, the voltage on the threshold input must exceed the control voltage or + 2/3 VCC. They also turn the discharge transistor on. To force the output from the timer high, the voltage on the trigger input must drop below +1/3 VCC. This also turns the discharge transistor off.A voltage may be applied to the control input to change the levels at which the switching occurs. When not in use, a 0.01 nano Farad capacitor should be connected between pin 5 and ground to prevent noise coupled onto this pin from causing false triggering.Connecting the reset (pin 4) to a logic low will place a high on the output of flip-flop. The discharge transistor will go on and the power amplifier will output a low. This condition will continue until reset is taken high. This allows synchronization or resetting of the circuit's operation. When not in use, reset should be tied to +VCC.
How comparators works?
A comparator(electronic such as an LM393*) works by sampling two input pins and turns on an output when there is ether a difference or similarity of the inputs. it depends on how the comparator is used int he design. Say you have a reference voltage on the "inverting"( - ) pin of 5 volts. And you have the "non-inverting" ( + ) connected to measure a voltage. when the voltage on the Non-inverting side equals the inverting voltage. the Output pin will turn on. Usually the Output Pin is open and will switch to ground once the comparator is activated. Remember since most all comparators have open-collector outputs, you will need the pull-up the pin to the source voltage through a resistor to see the switching action. To make the put act differently, (instead of switching to ground when active) all you need to do is exchange(swap) the input pins. See www.national.con for a datasheet on the LM393
Why is a Schmitt trigger called a regenerative comparator?
A Schmitt Trigger is a comparator, because it compares its input voltage to a "threshold" voltage, but it has _two_ threshold voltages (the upper and lower trigger voltages), and which threshold voltage is used depends on the output state. If the input voltage is higher than the upper trigger voltage, the output will be high (for a non-inverting Schmitt trigger). In this state, the input is compared to the lower threshold voltage, so the input now has to go below the lower threshold voltage before the output will go low. The threshold voltage depends on the output state, such that a high output selects the lower threshold voltage, and a low output selects the upper threshold voltage. This can be visualised as using a fixed threshold but adding a small voltage (the difference between the upper and lower threshold voltages, also called the hysteresis voltage) to the input voltage before it is compared. This small added voltage is high when the output is high, and low when the output is low. A small amount of the output voltage is effectively being added to the input voltage before it is compared to a fixed threshold. This is positive feedback, also called regenerative feedback. So a Schmitt trigger operates as a voltage comparator, and a small amount of the output is added to the input, so it uses positive or regenerative feedback.
What are the differences between a schmitt trigger and multivibrator?
comparator will change its state when the voltage exceeds a threshold it will return to the intial state when the voltage drops below this threshold.schmmit trigger will change its state when the voltage exceed a threshold and willl not return to the intial state until the voltage drops at a certain value below the initial threshold. The s the reluctance of the schmmit trigger. Something like inertia in mechanics. That's why Schmit trigger can oscillates. Something somehow similar to the negative resistance in diodes which make them oscillates.
What is the lowest stimulus voltage that induces active force in the skeletal muscle?
It is called the threshold voltage and is around -70 mvolts.
Why is the threshold voltage for nerve lower than the threshold voltage for muscle?
assignment sa physiology ceu? XD
Why is the threshold voltage for nerve lower than the threshold voltage for muscles?
assignment sa physiology ceu? XD
Difference between Threshold voltage and knee voltage?
the voltage at which electronic device operates is callled threshold voltageand the voltage at which device show cinduction in forward biased stste
What is a threshold voltage in scr?
the voltage at which the current conduction occur
What is mean by thresold voltage?
the device oprates on the minimum voltage. in this voltage is called threshold voltage.
What is threshold voltage of a muscle?
1.5
What is the voltage threshold for GAAs?
1.7 volts
What was the threshold voltage in activity 1?
3.0V
What is lower threshold voltage?
the voltage above which any device starts conducting
