1. What is the effect of adding a small resistor to the output of the op amp?
Answer: The output short-circuit protection method of the op amp is very simple. As long as a small resistor R is connected in series with the output of the op amp, as shown in the figure, the output short circuit can be prevented from failure. If this resistor is connected to the feedback loop, as shown by the dotted line in the figure, except that the output voltage drops significantly (2kΩ load, the figure can be reduced by 10% under the condition of the figure), it has no effect on the other performance of the circuit. .
This circuit also has the advantage that the circuit is also very stable for external capacitive loads. Therefore, a small resistor should be connected to the output of the op amp even if the integrated op amp has internal current limiting resistors.
2. Why are the external resistors of the op amps all of K-European grades? Why isn't the ohmic grades ah? For example, the inverse-phase proportional amplifier, Rf/Ri=10; general Rf=10k, Ri=1k; why Rf=1K, Ri=100 is not Europe?
A: This issue is related to power consumption. Although the small resistance noise is also small, but the power consumption increases, there are many problems:
1, the ground current increases. This may wish to consider its harm from the coupling of operational amplifiers at all levels, the ground current is large, and the ground potential difference between the stages will increase.
2 Resistor power consumption increases. It seems that people do not pay much attention to this understanding. In fact, taking Rf as an example, there is a voltage between the input and output, and this voltage will inevitably generate current in the resistor. If the 4V output, 10k resistance has 40mA, can not afford - you think about, how much output current of an op amp? With 100k resistance, only 4mA, the situation is completely different. Please note that on the second floor, Rf is actually part of the output load (impedance), which is to draw current from the output of the op amp.
3 Small resistance increases the source output impedance effect. The input impedance resistor Ri is often required to be as large as possible. The purpose is to try to avoid the influence of the source output resistance. Related theories can be found in books. From the perspective of the source, although the large loop current of the signal source can reduce the influence of noise, the small input impedance of the receiver also raises the problems of the source output impedance and the line impedance. Therefore, the input impedance should not be too small.
In general, the selection of these resistors involves some contradictory processing and a trade-off must be made.
Leather Bag
1.More than thousands designs on our website,new arrivals every week, you are sure to find products that you are interested in.
2.Rich variety of productsCombine your order with Real leather or PU leather women/men bag,wallet.
Purse,Evening bag, Clutch,Holder, Belt.
3. OEM and ODM order are acceptable, any kinds of logo printing or design are available.
4. We can make the sample first for you to check the design and quality before you place order.
5. All products pass inspection by our professional QC .
6. Good Quality + Factory Price + Quick Response + Reliable Service is what we are trying best to offer you.
7. All of our products are produce by our professional workmen and we have our high-work-effect foreign trade team, you can totally believe our quotation and service.
Leather Bags,Leather Bag,Protective Case,Protection Cover
Ysure Leather case 24/7 Support : 86 13430343455 , https://www.ysurecase.com