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Q2. Why is there a maximal allowable value?Rive said:Q1: that 'freewheeling' diode belongs to the relay, not related with the opamp. You do that to every relay, to handle the voltage spike when you switch off the relay.
Q2: the load (current, voltage) on the opamp output should be lower than the maximal allowable. The 'high' here depends on the type of the opamp.
Q3: that resistor belongs to the LED, not to the opamp. The current on the LED should be limited, according to the LED type & opamp output voltage.
Faiq said:Q2. Why is there a maximal allowable value?
Q3. My book stated that large currents through LED can damage both Op Amp (Because it is connected in series with LED) and the LED? Is that wrong?
Q2: It's what the actual device can/guaranteed to bear at most. The values are available in the device datasheet, or more likely: you will chose devices, which fits your design requirements.Faiq said:Q2. Why is there a maximal allowable value?
Q3. My book stated that large currents through LED can damage both Op Amp (Because it is connected in series with LED) and the LED? Is that wrong?
I don't have a datasheet. I am simply making questions regarding the statements made in a A Levels book.jim hardy said:How about if you post an opamp datasheet so we can show you where in that datasheet are the answers to your questions?
eg
View attachment 113669
Faiq said:n your example, does the term short circuit can also be replaced with high current?
http://www.ti.com/lit/an/sloa011/sloa011.pdfFaiq said:I don't have a datasheet. I am simply making questions regarding the statements made in a A Levels book.
Faiq said:I am simply making questions regarding the statements made in a A Levels book.
richard lareva said:Since you do not have the data sheet for these parts, you can assume that the LED has about a 2 volt forward bias drop. Subtract this voltage from your supply voltage, assume that the maximum safe forward biased current through the LED is about 20 milliamps, then solve for the value of "R" using the formula R=E/I, "E" being voltage and "I" being current. Any more questions feel free to ask.
Have you yet learned "ideal voltage source" ? It can deliver infinite current.Faiq said:Q3. Why should there be a resistor in between an LED and an Op Amp output?
Thank you very much for your perfect explanation. Please see if I understood this correctly. An amplifier has a zero output impendence, so the current coming out of an amplifier is very large. The large current can destroy an LED if a limiting resistor is not present.jim hardy said:I shouldn't have been short.
As rl says, we're unsure of your familiarity with basics. And we don't know how good are explanations in your A level book.
Have you yet learned "ideal voltage source" ? It can deliver infinite current.
Of course there's no such thing in the real world, but we do use ideal parts in our imaginary thought experiments.
So as rl explained , an ideal voltage source will deliver whatever current is necessary to satisfy its desired terminal voltage. That current might be quite large.
While that large current won't hurt an ideal part it sure could wreck a real one.
The opamp will do its best to mimic an ideal voltage source .
As a circuit designer you don't want your opamp to die trying, so you include in your circuit enough resistance to cause just the right current for just the right voltage. That protects both the opamp and the LED.
It's that simple.
old jim
No, it has a very low output impedance if it is any good, but not zeroFaiq said:An amplifier has a zero output impendence
That depends on the load and in any case is limited to the capability of the power source.so the current coming out of an amplifier is very large.
Yes, BUT only if it is created by a large voltage. Amplifiers normally amplify voltage, not current.The large current can destroy an LED if a limiting resistor is not present.
No, because the extra current is not being created out of thin air, it is coming from the power supply.A very low input current is fed to an amplifier and a very high current is obtained. Does this not violate Kirchoff's Law of Charge conservation?
If the Power supply is providing a current 1A, does this mean the highest value attainable by the current at output of amplifier is 1A?phinds said:No, because the extra current is not being created out of thin air, it is coming from the power supply.
Yes, but the way you phrased your question still implies some confusion. The power supply doesn't supply 1 amp unless it is needed, so the proper way to think of it is that the power supply is CAPABLE of supplying 1 amp, in which case the output of the amplifier is limited to 1 amp. And, really, the rest of the amplifier circuit will take some current to operate, so the output would be limited to something less than 1 amp.Faiq said:If the Power supply is providing a current 1A, does this mean the highest value attainable by the current at output of amplifier is 1A?
Ah so technically the power supply can supply any current, it just depend on the resistance of the whole circuit.phinds said:Yes, but the way you phrased your question still implies some confusion. The power supply doesn't supply 1 amp unless it is needed, so the proper way to think of it is that the power supply is CAPABLE of supplying 1 amp, in which case the output of the amplifier is limited to 1 amp. And, really, the rest of the amplifier circuit will take some current to operate, so the output would be limited to something less than 1 amp.
NO. The power supply can supply whatever current it is designed for. Within that limit, it can supply any amount from zero up to that amount. If the limit is 1 amp then that's all it can supply.Faiq said:Ah so technically the power supply can supply any current, it just depend on the resistance of the whole circuit.
Oh yeah right. Thank you very much for clarifying this.phinds said:NO. The power supply can supply whatever current it is designed for. Within that limit, it can supply any amount from zero up to that amount. If the limit is 1 amp then that's all it can supply.
Faiq said:Oh yeah right. Thank you very much for clarifying this.
Faiq said:Oh yeah right. Thank you very much for clarifying this.
But you did it again in this thread, is why I was pointing it out.Faiq said:Yeah I notified the moderator, he fixed the problem.
An opamp, short for operational amplifier, is an electronic component that amplifies the difference between two input voltages. It consists of a high-gain differential amplifier and other components that allow it to perform mathematical operations such as addition, subtraction, multiplication, and integration.
Opamps are used in a wide range of electronic circuits, including audio amplifiers, filters, oscillators, comparators, and voltage regulators. They are also commonly used in signal processing, instrumentation, and control systems.
An ideal opamp has infinite open-loop gain, infinite input impedance, zero output impedance, and zero input offset voltage. It also has infinite bandwidth and can handle infinite input signal levels without distortion.
The selection of an opamp depends on the specific requirements of your circuit, such as the desired gain, bandwidth, input and output impedance, and power supply requirements. It is important to carefully read the datasheet and compare different opamps before making a selection.
Opamp circuits can be analyzed using basic circuit analysis techniques, such as Kirchhoff's laws and Ohm's law. Troubleshooting opamp circuits involves checking for proper power supply voltages, input and output signals, and component values. It is also important to check for proper grounding and connections. Using simulation software can also help in analyzing and troubleshooting opamp circuits.