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Op Amp Applications Handbook Be the first to review this product. Skip to the end of the images gallery. Skip to the beginning of the images gallery. A OL is the open-loop gain.
Operational Amplifier Circuits & Applications
The impedance of the signal sources connected to the input of an op-amp must be very much smaller than the amplifier input impedance to avoid signal loss. An ideal op-amp has zero output impedance. This means that the output voltage is independent of output current. Thus an ideal op-amp can act as a perfect internal voltage source with zero internal resistance, so that maximum current can be driven to the load.
Practically, the output impedance of the op-amp is affected by the negative feedback and is given by,. Load impedances connected at the output of the op-amp must be much larger than the circuit output impedance, to avoid any significant loss of output as a voltage drop across Z out.
Open-loop gain of an op-amp is defined as the gain of the op-amp when there is no feedback from the output to either of its inputs. For an ideal op-amp, the gain will be infinite theoretically, but practical value range from 20, to , An ideal op-amp can amplify any frequency signal from DC to highest AC frequencies, thus it has an infinite frequency response.
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Therefore, the bandwidth of an ideal op-amp should be infinite. In practical circuits, the bandwidth of the op-amp is limited by the gain-bandwidth product GB. CMRR is defined as the ability of an op-amp to reject the common mode input signal.
CMRR is an important measure of an op-amp. An ideal op-amp will have infinite CMRR. In practical circuits, CMRR is given by. Where, A D is the differential gain and A C is the common mode gain of the op-amp. The input offset voltage defines the differential DC voltage required between the input terminals to make the output zero volts with respect to ground. An Ideal op-amp will have zero offset voltage, whereas practical op-amps show some small offset.
Slew rate is defined as the maximum change of output voltage per unit time and is expressed as volts per second. An ideal op-amp will have an infinite slew rate. In practical op-amps, the slew rate is inherently limited by the small internal drive currents of the op-amp and also by the internal capacitances designed to compensate for high frequency oscillations. The open loop gain A OL is not constant for all frequencies. Real op-amps have a frequency-dependant open-loop gain.
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The frequency response curve of a practical op-amp is as shown below. From the above curve, we can note that the product of gain and frequency is constant at any point along the curve. This constant is known as the Gain-Bandwidth product GB. Also, the gain of the amplifier at any point along the curve is determined by unity-gain 0 dB frequency. The bandwidth of the operational amplifier is defined as the frequency range over which the voltage gain of the amplifier is above -3dB maximum is 0dB of its maximum output value.
In the above figure, the -3dB of the A V max is shown as 37dB. The 37dB line intersects with the curve at just over 10 kHz frequencies. This frequency can be more accurately calculated if the GB product of the amplifier is known. It can be noted that the open-loop gain decreases as the frequency of the input signal increases. Frequency is plotted in logarithmic scale and the gain decreases linearly as frequency increases logarithmically.
The rate of fall of the gain in op amp is known to be 20 dB per decade. Operational amplifiers are popular building blocks in electronic circuits and they find applications in most of the consumer and industrial electronic systems. Op-amps can be configured to work as different types of signal amplifiers like inverting, non-inverting, differential, summing, etc.
Operational amplifiers can be used in construction of active filters, providing high-pass, low-pass, band-pass, band-reject and delay functions. The high input impedance and gain of an op-amp allow straightforward calculation of element values, allows accurate implementation of any desired filter topology with little concern for the loading effects of stages in the filter or of subsequent stages.
An operational amplifier can, if necessary, be forced to act as a comparator. The smallest difference between the input voltages will be amplified considerably.
Op-amps are used in the construction of oscillators, like an Wein bridge oscillator. Op-amps are also used in non-linear circuits such as logarithmic and anti-logarithmic amplifiers.
Applications of Differntial Amplifiers in Electronics
Op-amps are also used in signal processing circuits such as Precision Rectifiers, Clamping circuits and Sample-and-Hold circuits. An operational amplifier is a very high gain DC differential amplifier. Most op-amps require both positive and negative power supply to operate. Op-amps can be configured through one or more external feedbacks and voltage biases to obtain desired responses and characteristics.
The basic op-amp construction is of a three terminal device, excluding power connections. Op-amps sense the difference between the voltage signals applied at their input terminals and then amplify it by some pre-determined gain. Closing the open loop by connecting a resistive or reactive component between the output and one input terminal of the op-amp greatly reduces and controls this open-loop gain. An ideal op-amp has infinite open-loop gain, infinite input impedance, zero output impedance, infinite bandwidth, infinite slew rate and zero offset.
A practical op-amp exhibits high open-loop gain, high input impedance and low output impedance. Because of their versatile uses Op-amps are used in conjunction with resistors and capacitors to build functional circuits such as Inverting, Non-inverting, voltage following, summing, subtracting, integrating and differentiating type amplifiers. In this tutorial, we will learn about Operational Amplifiers in general, its characteristics, few applications and some of the important Operational Amplifier Basics. Operational Amplifier or simply Op-amp is one of the most frequently and widely used electronic component.
They are the main building blocks in Analog Circuits and are used in a wide range of consumer electronics, industrial equipment and scientific devices.
Applications of Differential Amplifiers
Transistors Q1 and Q2 forms a differential amplifier, where the difference input voltage is applied to the base terminals of Q1 and Q2. The two input signals Vi1 and Vi2 are applied to the base terminals of Q1 and Q2 respectively.
Zo is the output impedance of op-amp without feedback. AOL is the open-loop gain. Load impedances connected at the output of the op-amp must be much larger than the circuit output impedance, to avoid any significant loss of output as a voltage drop across Zout.