views on op amps

  1. jeffrey samuel
    jeffrey samuel
    let us see

    what is an op amp?

    what are its features ?

    its prime role?

    do post all your suggestions with pictures if possible

    all suggestions will be encouraged
  2. rfredel
    rfredel
    What is an op amp?
    An OP amp is a DC amplifier with high voltage gain and differential input and a single - ended output.

    Op amps were developed as computing amplifiers between 1939 and 1941 by Bell Labs to use in radar controlled wapons. These op amps were made of electronic tubes and diskret devices.

    After WW II George A. Philbrick Researches Inc. (GAP/R) developed a "Modul" with two tubes (12AX7). These Moduls need a operations voltage of +/- 350V and the amplification was 90dB.


    In 1961 GAP/R developed an op amp with germanium transistors on a PCB. these op amps were better than the tube moduls, because the only need a rail to rail voltage of +/- 15V and have a gain of 94dB.


    Today everyone knows op amps as ICs. This ICs were developed by "Fairchild Semmiconductors" in 1962. This typ was ľA702, followed by ľA709 in 1965 and ľA741 in 1968.

    This ľA741 was the built by the most semiconductor producers.

    Here you see the inside circuit diagram of a typical op amp in BJT technics.


    Today there are a lot of op amps in different technics, like BFT, JFET an Mosfet, aviable.


    What are its features?
    The features of a op amp are:
    1. differential inputs ( non inverting and inverting input)
    2. high open loop amplification
    3. programmable gain (closew-loop amplification) by only two resistors
    4. DC amplification
    5. For some types are special offset adjust inputs are existing.
    6. Only five pins for connecting are nessesary. (inverting input, non - inverting input, output, positive supply voltage, negative supply voltage or ground)
    7. High frequency range ( special types goes up to GHz - range)
    8. Constant gain over the bandwidth
    9. Low noise
    10. Special types, like comparators and audio amps, are aviable.
    11. Very high input resistance at the non-inverting input.
    12. Zero Ohm at the inverting input. So it can use as summing input with only one resistor at each input.
    13. Low output resistance and high output voltage swing.


    What is it s prime role?
    The prime role of an op amp is, that you can build very small amps with a less of devices. You can design amps with low noise, high gain and wide bandwidth .
  3. jeffrey samuel
    jeffrey samuel
    Nice a complete guide to all the role and development of OP amps thank you friend
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