Chapter 5 Operational Amplifiers (original) (raw)
Operational Amplifier UNIT 1 Electronic Circuit BTECH 2ND YR BY Mr. Amit Kumar Kesarwani
As well as resistors and capacitors, Operational Amplifiers, or Op-amps as they are more commonly called, are one of the basic building blocks of Analogue Electronic Circuits.Operational amplifiers are linear devices that have all the properties required for nearly ideal DC amplification and are therefore used extensively in signal conditioning, filtering or to perform mathematical operations such as add, subtract, integration and differentiation. An Operational Amplifier, or op-amp for short, is fundamentally a voltage amplifying device designed to be used with external feedback components such as resistors and capacitors between its output and input terminals. These feedback components determine the resulting function or " operation " of the amplifier and by virtue of the different feedback configurations whether resistive, capacitive or both, the amplifier can perform a variety of different operations, giving rise to its name of " Operational Amplifier ". An Operational Amplifier is basically a three-terminal device which consists of two high impedance inputs, one called the Inverting Input, marked with a negative or " minus " sign, (and nd the other one called the Non-inverting Input, marked with a positive or " plus " sign (+). The third terminal represents the Operational Amplifiers output port which can both sink and source either a voltage or a current. In a linear operational amplifier, the output signal is the amplification factor, known as the amplifiers gain (A) multiplied by the value of the input signal and depending on the nature of these input and output signals, there can be four different classifications of operational amplifier gain. • Voltage – Voltage " in " and Voltage " out " • Current – Current " in " and Current " out " • Transconductance – Voltage " in " and Current " out " • Transresistance – Current " in " and Voltage " out " Since most of the circuits dealing with operational amplifiers are voltage amplifiers, we will limit the tutorials in this section to voltage amplifiers only, (Vin and Vout). The output voltage signal from an Operational Amplifier is the difference between the signals being applied to its two individual inputs. In other words, an op-amps output signal is the difference between the two input signals as the input stage of an Operational Amplifier is in fact a differential amplifier as shown below. Differential Amplifier The circuit below shows a generalized form of a differential amplifier with two inputs marked V1and V2. The two identical transistors TR1 and TR2 are both biased at the same operating point with their emitters connected together and returned to the common rail,-Vee by way of resistor Re.
Operational Amplifier by Amit Kumar Kesarwani
Operational amplifiers one of the basic building blocks of analog electronics. For our purposes we will be using an ideal model of the op amp. The circuit symbol for an op amp is shown.
An operational amplifier (abbreviated op-amp) is an integrated circuit (IC) that amplifies the signal across its input terminals. Op-amps are analog, not digital, devices, but they are also used in digital instruments. Op-amps are widely used in the electronics industry, and are thus rather inexpensive -the ones used in the lab are about $0.25 each! In this learning module, no details are given about the internal structure of the op-amp. Rather, we summarize many useful applications of op-amps.
Operational Amplifier Circuits Review: Ideal Op-amp in an open loop configuration
Ip In An ideal op-amp is characterized with infinite open–loop gain A → ∞ The other relevant conditions for an ideal op-amp are: 1. 0 Ip In = = 2. Ri = ∞ 3. 0 Ro = Ideal op-amp in a negative feedback configuration When an op-amp is arranged with a negative feedback the ideal rules are: 1. : input current constraint 0 Ip In = = 2. : input voltage constraint Vn Vp = These rules are related to the requirement/assumption for large open-loop gain , and they form the basis for op-amp circuit analysis.