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الموضوع: the operation amplifier

  1. #1
    Junior Engineer
    تاريخ التسجيل
    Mar 2006
    الدولة
    أ£أ•أ‘
    المشاركات
    6

    the operation amplifier

    the operation amplifier
    هو جهاز الكتروني صغير يستخدم لتكبير الدخل
    انواع الoperation amplifier
    1_inverting operation amplifier{يكبر الدخل مع تغيير اشارته اي ان الجزء الموجب في الدخل يصبح سالب في الخرجوالعكس}
    2_non inverting operation amplifier{يكبر الدخل دون تغيير في اشارته}
    استخداماته
    *يستخدم كجهاز تفاضلي اي اذا كان الدخل داله تربيعيه فان الخرج يكون خط مستقيم
    *يستخدم كجهاز تكاملي اي يكامل الدخل
    ملحوظه:الدخل ممكن ان يكون موجه جيبيه او موجه علي شكل سن المنشار
    اتمني ان تتقبلوا مني هذه المعلومه
    واذا كانت هناك ملاحظات اتمني ان توضحوها

  2. #2
    Junior Engineer الصورة الرمزية على حمدى
    تاريخ التسجيل
    Jan 2006
    الدولة
    zagazig
    المشاركات
    136

    مشاركة: the operation amplifier

    An operational amplifier, often referred to as an 'op-amp', is a DC-coupled electronic differential voltage amplifier, usually of very high gain, with one inverting and one non-inverting input. The single output voltage is the difference between the inverting and non-inverting inputs multiplied by the open-loop gain:


    The amplifier's output can be single-ended or, less often, differential. Circuits using op-amps almost always employ negative feedback. Because the op-amp has such high gain, the behavior of the amplifier is almost completely determined by the feedback elements.

    The ideal op-amp
    For any input voltages the ideal op-amp has infinite open-loop gain (see also gain), infinite bandwidth, infinite input impedances (and hence zero input currents), zero output impedance, zero noise, and zero input offset voltage (exactly 0 V out when both inputs are equal). Real op-amps can only approximate to this ideal, and the actual parameters are subject to drift over time and with changes in temperature, input conditions, etc.

    Modern integrated FET or MOSFET op-amps approximate more closely to these ideals than bipolar ICs where large signals must be handled at room temperature over a limited bandwidth; input impedance, in particular, is much higher.

    Where the limitations of real devices can be ignored, an op-amp can be viewed as a black box with gain; circuit function and parameters are determined by feedback, usually negative. IC op-amps as implemented in practice are moderately complex integrated circuits

    Limitations of real op-amp implementations
    DC imperfections:

    Finite gain — the effect is most pronounced when the overall design attempts to achieve gain close to the inherent gain of the op-amp.
    Finite input resistance — this puts an upper bound on the resistances in the feedback circuit. Some op-amps have circuitry to protect inputs from excessive voltage: this makes input parameters slightly worse. Some op-amps are available in protected (thus slightly degraded) and unprotected versions.
    Nonzero output resistance — important for low resistance loads. Except for very small voltage output, power considerations usually come into play first.
    Input bias current — a small amount of current (typically ~10 nA for bipolar op-amps, or picoamperes for CMOS designs) flows into the inputs. This current is mismatched slightly between the inverting and non-inverting inputs (there is an input offset current). This effect is usually important only for very low power circuits.
    Input offset voltage — the op amp will produce an output even when the input pins are at exactly the same voltage. For circuits which require precise DC operation, this effect must be compensated for; many practical op-amps have an offset compensation input.
    AC imperfections:

    Finite bandwidth — all amplifiers have a finite bandwidth. However, this is more pronounced in op amps, which use internal frequency compensation to avoid unintentionally producing positive feedback due to parasitic capacitance.
    Input capacitance — most important for high frequency operation.
    Nonlinear imperfections:

    Saturation — output voltage is limited to a peak value, usually slightly less than the power supply voltage.
    Slew rate — the rate of change of the output voltage is limited (usually by the internal compensation used)
    Non-linear transfer function — The output voltage may not be accurately proportional to the difference between the input voltages. This effect will be very small in a practical circuit if substantial negative feedback is used.
    Power considerations:

    Limited output power — if high power output is desired, an op-amp specifically designed for that purpose must be used. Most op-amps are designed for low power operation and are typically only able to drive output resistances down to 2 kΩ.
    Limited output current — the output current must obviously be finite. In practice, most op-amps are designed to limit the output current so as not to exceed a specified level—around 25 mA for a type 741 IC op-amp—thus protecting the op-amp and associated circuitry from damage

  3. #3
    Junior Engineer الصورة الرمزية على حمدى
    تاريخ التسجيل
    Jan 2006
    الدولة
    zagazig
    المشاركات
    136

    مشاركة: the operation amplifier

    Modern op-amps
    General-purpose integrated op-amps of standard specification sell for well under one U.S. dollar. Modern designs are electronically more rugged than earlier implementations; some can sustain direct short-circuits on their outputs without damage
    .Use in electronics system design
    The use of op-amps as circuit blocks is much easier and clearer than specifying all their individual circuit elements (transistors, resistors, etc.), whether the amplifiers used are integrated or discrete. In the first approximation op-amps can be used as if they were ideal differential gain blocks; at a later stage limits can be placed on the acceptable range of parameters for each op-amp.

    Circuit design follows the same lines for all electronic circuits. A specification is drawn up governing what the circuit is required to do, with allowable limits. For example, the gain may be required to be 100 times, with a tolerance of 5% but drift of less than 1% in a specified temperature range; the input impedance not less than 1 megohm; etc.

    A basic circuit is designed, often with the help of circuit modelling (on a computer). Specific commercially available op-amps and other components are then chosen that meet the design criteria within the specified tolerances at acceptable cost. If not all criteria can be met, the specification may need to be modified.

    A prototype is then built and tested; changes to meet or improve the specification, alter functionality, or reduce the cost, may be made.

  4. #4
    Junior Engineer الصورة الرمزية على حمدى
    تاريخ التسجيل
    Jan 2006
    الدولة
    zagazig
    المشاركات
    136

    مشاركة: the operation amplifier

    DC behaviour
    Open-loop gain is defined as the amplification from input to output without any feedback applied. For most practical calculations, the open-loop gain is assumed to be infinite; in reality it is obviously not. Typical devices exhibit open-loop DC gain ranging from 100,000 to over 1 million; this is sufficiently large for circuit gain to be determined almost entirely by the amount of negative feedback used. Op-amps have performance limits that the designer must keep in mind and sometimes work around. In particular, instability is possible in a DC amplifier if AC aspects are neglected.


    AC behaviour
    The op-amp gain calculated at DC does not apply at higher frequencies. To a first approximation, the gain of a typical op-amp is inversely proportional to frequency. This means that an op-amp is characterized by its gain-bandwidth product. For example, an op-amp with a gain bandwidth product of 1 MHz would have a gain of 5 at 200 kHz, and a gain of 1 at 1 MHz. This low-pass characteristic is introduced deliberately, because it tends to stabilize the circuit by introducing a dominant pole. This is known as frequency compensation.

    Typical low cost, general purpose op-amps exhibit a gain bandwidth product of a few megahertz. Specialty and high speed op-amps can achieve gain bandwidth products of hundreds of megahertz. For very high-frequency circuits, a completely different form of op-amp called the current-feedback operational amplifier is often used.

  5. #5
    Junior Engineer الصورة الرمزية على حمدى
    تاريخ التسجيل
    Jan 2006
    الدولة
    zagazig
    المشاركات
    136

    مشاركة: the operation amplifier

    انتظروا المزيد ان شاء الله

  6. #6
    Junior Engineer الصورة الرمزية على حمدى
    تاريخ التسجيل
    Jan 2006
    الدولة
    zagazig
    المشاركات
    136

    مشاركة: the operation amplifier

    Operational amplifier applications
    http://en.wikipedia.org/wiki/Operati...r_applications

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