Operational Amplifier

The history of the operational amplifier The first use of vacuum tube amplifier design completed in about 1930 years ago, this amplifier can perform add and work. The first operational amplifier is designed purpose is to voltage analog to digital, used to add, subtract, multiply, and divide operations, but also a analog computer (analog computer) of the basic building blocks. However, the ideal op-amp circuit system design purposes is far more than addition and subtraction multiplication and division calculations. Today's op-amp, whether using transistors or vacuum tubes, discrete components or integrated circuit components, op amps have performance approaching the ideal op amp requirements. Early op amp is to use vacuum tube design, and now most of the IC-type components. However, if the demand exceeds the system for integrated circuit amplifier amplifier requirements, often using discrete components to achieve these special specifications of operational amplifiers.
 The late 1960s, Fairchild Semiconductor introduced the first widely used integrated circuit operational amplifier, model μA709, the designer is Bob Weller (Bob Widlar). But then came the 709 soon to be replaced by new products μA741, 741 has better performance, more stable, easier to use. 741 op-amp into the history of the development of micro-electronics industry a unique symbol, after decades of evolution has not been replaced, many IC manufacturers still in production 741. Until today μA741 is still the Department of Electronic Engineering in principle to explain a typical op amp materials. Op amp works Op amp has two inputs in Figure a (inverting input), b (in-phase input) and an output o. Were also referred to as the side of the input non-backward input and output. When the voltage increases in a U-side and public side (public side is the voltage zero point, which is equivalent to the circuit reference node.) Between the actual direction and its end is higher than from a public terminal, the output voltage U is the actual direction of the side from the common point o, namely, the two opposite direction. When the input voltage U + added to the b-side and between the public side, U and U + between the actual direction of the relatively common side exactly the same. For the sake of distinction, a side and b-side were used to "-" and "+" sign marked, but do not mistake them the direction of the positive and negative polarity voltage reference. Voltage of negative polarity should be marked or the other indicated by arrows. Generally regarded as a simple op amp: output port has a signal (Out) and the same phase, reversed-phase high-impedance inputs of two high-gain direct-coupled voltage amplifier unit, so the op amp can be used to produce the same phase, inverting and differential amplifier . Op amp power supply dual power supply points with a single supply two. For dual-supply op amp, the output voltage can be zero on both sides of the change in the zero differential input voltage output can be set to zero. Single supply op amp, the output power and changes to a range between.
 Op amp's input requirements than the negative power supply potential is usually a certain value, but lower than the positive supply a certain value. Specially designed to allow input of op amp can power potential in the negative to a positive supply from the whole range of changes, or even slightly above the positive supply or slightly below the negative supply is also allowed. Such as rail to rail op amp (rail-to-rail) input op amp. Op amp's output signal and two input voltage signals proportional to the difference in the audio section are: output voltage = A0 (E1-E2), which, A0 is the low-frequency op amp open loop gain (eg 100dB, that is 100,000 times) , E1 is the input signal with the phase voltage, E2 is the inverting input signal voltage.