KA7905 DATASHEET PDF

However, the fault does not occur for commonly used input voltages. Consumption no load Consumption 1k load Dattasheet 2. However, we think it necessary to inform our readers about fundamental faults and errors of electronics components that can cost a lot of time. Figure shows the dependencies of the output voltage on datashet input voltage for a L, TAS, KA; both with and without a 1k load.

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However, the fault does not occur for commonly used input voltages. Consumption no load Consumption 1k load Dattasheet 2. However, we think it necessary to inform our readers about fundamental faults and errors of electronics components that can cost a lot of time. Figure shows the dependencies of the output voltage on datashet input voltage for a L, TAS, KA; both with and without a 1k load.

The 79xx voltage regulators series made by ST have to be connected to a load consuming at least 5 mA. We believe that the entire problem is caused by inadequate values of resistors between the input and the output. We do our own development, too, and we do understand that it is not that easy to design and document something. The negative voltage was used to power operational amplifiers on a second board as well. PDF datasheet of a 79xx by National Semiconductors.

Unfortunately, we could not get a sample to measure. After a closer examination, I have found V at its reference input, instead of expected -8V. A similar internal schematic ka there; however, the values of the components are legible. It was not necessary to graph such a characteristics for a MC since the output voltage remained almost constant. Output VA characteristics of a L Values measured The comparison in this article is not totally objective. There is no such information in L79xx datasheets see picture way above.

So, we examined the datasheets more closely. At the very end ofthe Czech subsidiary of ST has informed us that information about this behavior will be included in a future update of the respective datasheets. At first, we came to a wrong conclusion, that the faulty stabilizers are sold at GM Electronic only, and we have released this information prematurely.

We have tried several different capacitors ranging from 15 nF to 1 uF, measured values were not significantly affected. Figure shows dependence of the output voltage on the input voltage for a L and a MC with no load, and with approx.

The table clearly indicates a distinctly lower consumption of the negative ST stabilizer. Stabilizers by ST differ, beginning from a certain voltage.

So, keep this possibility in mind when designing your own applications. The comparison is only an example what dataaheet developer can buy in an electronics components store.

Then, we have studied carefully the datasheets. The whole thing worked about a year or so. This is probably the cause of the problem. Values shown were measured for a single sample; other samples as well as stabilizers by other manufacturers behaved similarly. The ST stabilizer is clearly distinct. If this is an intention to reduce internal consumption of the circuit to a minimum, at the expense of problems with output voltage with no load, it should have been mentioned in the datasheet.

Conclusion is, that oscillations are not the cause of our overvoltage problem. However, components by other manufacturers behave differently. There, they do clearly state that the output voltage is guaranteed in a certain load current range; however, there is NO warning, that a voltage four times higher than the nominal output can appear at the output pin. KA Datasheet Recommended operating circuit is shown. As I have said at the beginning of this article, I believe this fault is significant enough that we should inform about it.

Here, minimum load current is specified: If ST really does use such an internal structure, the problem is most likely caused by unsuitable values of resistors around the 6. Possible cause of the problem: Again, there was V. For comparison, input current of a positive voltage stabilizer is mentioned, too. The ST company can argue that this is possible; however, that the voltage from The rest of this article ia the fact, that: May — 0: Some time ago, I used a pair of and to generate symmetrical reference voltage in my circuit.

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KA7905 Fairchild Semiconductor, KA7905 Datasheet

Mizilkree The whole thing worked about a year or so. Daatasheet shows the dependencies of the output voltage on the input voltage for a L, TAS, KA; both with and without a 1k load. Nothing like that is there. We believe that the entire problem is caused by inadequate values of resistors between the input and the output. Stabilizers by ST differ, beginning from a certain voltage. This is true, BUT: Values shown were measured for a single sample; other samples as well as stabilizers by other manufacturers behaved similarly. Two stabilizers were used for comparison.

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KA7905 Fairchild Semiconductor, KA7905 Datasheet - Page 8

Output VA characteristics of a L Values shown were measured for a single sample; other samples as well as stabilizers by other manufacturers behaved similarly. Recommended operating circuit is shown. KA Datasheet — So, keep this possibility in mind when designing your own applications. Values listed below were measured using a nF capacitor. The situation is similar with other stabilizers. The internal schematics of 79xx and 78xx are very different you can see both internal schematics in datasheets, which are included at the end of this article. The comparison in this article is not totally objective.

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KA7905 Fairchild Semiconductor, KA7905 Datasheet - Page 3

Gucage Values shown were measured for a single sample; other samples as well as stabilizers by other manufacturers behaved similarly. Conclusion is, that oscillations are not the cause of our overvoltage problem. Well, I bought a new L by ST. There, they do clearly state that the output voltage is guaranteed in a certain load current range; however, there is NO warning, that a voltage four times higher than the nominal output can appear at the output pin. This is true, BUT: So, keep this possibility in mind when designing your own applications. Unfortunately, we could not get a sample to measure.

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