Recent content by brutus

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    PWM filter... does it matter which cap?

    Hi, I want to change a PWM into a smooth analog signal. I have the circuit, but I was wondering if it mattered what capacitor I would be using. I want to use a ceramic cap... does it matter? The PWM is a 100 KHz square wave.
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    LDO Loop Compensation (question)

    Hi, I'm reading the following pdf: http://www.national.com/an/AN/AN-1482.pdf Can someone explain what a pole is? "The capacitor connected to the ouput formsa pole with the load resistor whose frequency is given by" and so on... What is a Load Pole. I'm a layman, so please "dim it down a...
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    Voltage Regulator Question

    Thanks! I will do that. I was a bit unclear... I meant the chip maker of the Qt301 that needs a ceramic cap for high frequency supression, not the regulator. Anyways... this has been most educational. I appreciate your help.
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    Voltage Regulator Question

    Yes. You are right. The guy from the chip company said: "ceramic capacitors are needed for high frequency supression" He said this regarding the chip I need to 'voltage regulate' Will adding a 1 Ohm resistor in series to the ceramic cap solve this problem, and would it affect the ceramic...
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    Voltage Regulator Question

    Hi, I just spoke to the guys that make the chip (that I need to 'voltage regulate') as well as a tech guy from digikey who knew about this issue. They both said that this issue was true in the past (1980's 1990's) but is no longer an issue at all because the LDOs have internal components to...
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    Voltage Regulator Question

    > Even additional ceramic caps on the output cause trouble. Ok... Does this mean that any cap that is between the supply voltage (in this case the output of the regulator) and Ground can cause problems? _BUT_ Capacitors that are in other parts of the circuit (are not directly connected to...
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    Voltage Regulator Question

    Hi, I read an article about LDO and mistakes people make that result in an unstable output. http://www.national.com/nationaledge/jul02/article2.html In that article (which is way over my head) they mention that tantalum and ceramic are not compatible (or something). I will post the two...
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    Voltage Regulator Question

    >I assume you are trying to use as little board space as possible? I design with "surface mount" tantalums instead of "through hole" Electrolytics in such a case. Solves many other problems as well. You assume correctly, except it's not only board space but I also need a very low profile...
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    Voltage Regulator Question

    >It is a nice regulator, but: >Can you buy a 2.2uF capacitor that is guaranteed to be at least 2.2uF? >Did you notice that every example circuit in the datasheet has a 10uF output >capacitor? Ok... So I'll use a 10uF outpur cap... Solves the overshoot problem maybe? I still want to...
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    Voltage Regulator Question

    Hmmm.... 100uF seems really high... Attached is a JPEG of the "test circuit" where they use 2.2 uF instead of 100uF. The whole pdf document can be found at: http://www.st.com/stonline/books/pdf/docs/2573.pdf Am I missing something? B
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    Voltage Regulator Question

    Thanks for the reply. I did find a circuit. It uses a 0.1uF for the input film capacitor (poly...ester?), and a 2.2uF electrolytic capacitor for the output. Final question: Do I really need to use an electrolytic cap? They are too big. I would prefer to use something smaller, maybe another...
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    Voltage Regulator Question

    Where do I say that I want to use a 78L05??? I say I dont. I want to use something like 78L033 or 78L04, except in a TO-92 package. Anyway... read my post if you're interested in replying...
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    Voltage Regulator Question

    Hi, In the data sheet for a chip (qt301 from qprox.com) I am using it says the following: "If the power supply is shared with another electronic system, make sure the supply is free of spikes, sags, and surges. The supply is best locally regulated using a conventional 78L05 type regulator, or...
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