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    General Purpose Op-amp

    Hi all,

    I have been using IC 741 in my circuits and just recently found that 741 has become old with bad specs in terms of Bandwidth etc....I do not mean to say it has become obsolete,it is still usable & a very good op-amp.
    But which op-amp would be best suited to replace Ic 741.I'm talking about in general all specs, bandwidth,gain at high freq.,slew-rate,power,voltage-swing???
    Would LM 358 fit the above cause ???

    regards.
    Last edited by rahdirs; 2nd June 2013 at 10:27.
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    Re: General Purpose Op-amp

    LM358 has the advantage of working in single-supply applications, input common range including negative rail, output voltage near to negative rail. But due to class B output stage it shows considerable crossover distortions which make it at bad choice for audio applications.

    Personally, I've been using TL071 (and the respective dual and quad devices) for standard applications since "ever", which outcompetes uA741 in effectively any specification (except for a slightly higher offset voltage of the cheapest standard variant). And LM358/LM324 for single supply or low power applications that don't need TL071 gain linearity, low input current and low noise.


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    Re: General Purpose Op-amp

    I like CA3140, CA3240, CA3160;
    CA3130 is faster but can require
    external frequency compensation.

    NE5532 and NE5534 are fast, low cost and very
    good for audio and general purpose
    but not for single-supply operation.



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    Re: General Purpose Op-amp

    Quote Originally Posted by aProgrammer View Post

    NE5532 and NE5534 are fast, low cost and very
    good for audio and general purpose
    but not for single-supply operation.
    Hi aProgrammer,

    why not for single-supply operation? Do you have corresponding experience?



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    Re: General Purpose Op-amp

    Quote Originally Posted by LvW View Post
    Hi aProgrammer,

    why not for single-supply operation? Do you have corresponding experience?
    because input common range don't include negative rail



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    Re: General Purpose Op-amp

    I agree that NE5532 and TL071/2/4 are good, low cost opamps.

    Here's something to bear in mind when choosing an opamp for a particular circuit: As a rule of thumb, JFET-input opamps (e.g. TL072) generally have higher input offset voltage and higher voltage noise than BJT-input opamps (e.g. NE5532). However they have lower input offset current and lower current noise.

    Thus JFET-input opamps tend to be best for circuits with high source impedance, while BJT-input opamps tend to be better for circuits with low source impedance.

    - - - Updated - - -

    Quick comparison of typical values:

    NE5532 TL074
    Voltage noise 5nV/SQRT(Hz) 18nV/SQRT(Hz)
    Current noise 0.7pA/SQRT(Hz) 0.01pA/SQRT(Hz)
    Input offset voltage 0.5mV 3mV
    Input offset current 10nA 5pA
    Last edited by godfreyl; 2nd June 2013 at 12:48.



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    Re: General Purpose Op-amp

    @FvM: I see in the data-sheet of LM 358 that "Differential Input Voltage Range Equal to Maximum-Rated Supply Voltage . . . 32 V".
    Does this mean if i'm using LM 358 with single supply of 32 V,can i apply input voltage of 0 V or 32 V????
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    Re: General Purpose Op-amp

    Does this mean if i'm using LM 358 with single supply of 32 V,can i apply input voltage of 0 V or 32 V????
    It means in other words that any voltage level within power supply rails is permitted for both input terminals. This is of course a maximum ratings specification and doesn't say anything about reasonable operation conditions, e.g. common mode range.

    It should be mentioned, that BJT input stages don't neccessarily tolerate high differential input voltages because they might exceed the reverse Vbe rating. Some OPs have dedicated protection circuits to protect the input stage, e.g. utilizing clamping diodes. Others like ľA741 or LM358 use a circuit topology with higher reverse rating. In "normal" amplifier operation, the differential input voltage is about zero, so you probably never activate this clamping circuit.


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    Re: General Purpose Op-amp

    A 741 is 45 years old. It was designed for a 30V supply and for DC and low frequencies. Audio was not considered but maybe for telephone quality.
    An LM358 or LM324 are also very old but they were the FIRST low power opamps. Therefore they have crossover distortion and work poorly above 2kHz. They are also noisy (hisssss).

    A TL07x is selected for low noise and works with a supply from 7V to 36V. It has very low distortion and works perfectly up to 100kHz.
    Millions of them are used in audio products so they are inexpensive.



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