Summing Amplifier

3 Key excerpts on "Summing Amplifier"

• 

  eBook - PDF

  Analog and Hybrid Computing

  The Commonwealth and International Library: Electrical Engineering Division

  • D. E. Hyndman, N. Hiller(Authors)
  • 2016(Publication Date)
  • Pergamon

    (Publisher)

  Summation, multiplication by a constant and sign inversion. For these operations the operational amplifier is set up as shown in Fig. 2.2, with a resistor R 0 as the feedback element, and the input connected by resistors R l9 R 2 , ..., R n to corresponding voltage sources e l9 e 2 , ...,e n . Consider the specification of the amplifier as being ideal except for the gain which we will take equal to — k. e 2 (2.2) (2.3) FIG. 2.2. Summing unit. If the amplifier has infinite input impedance, no current flows into it, and therefore the sum of the currents in the resistors R l9 R 2 , ...,i?„ must equal the current in the feedback resistor R 0 . If the voltage at the input of the amplifier, which is generally referred to as the summing junction, is e i9 then equating the currents in the resistors R 0 , R i9 ..., R n using Ohm's law, we get Ρι-*Γ| p2-gH P~ g 'l = Γ**-*ο1 L R ± yi R 2 y - l R„ j I Ro ] (2.1) Now Giving e 0 = -ke t to 18 ANALOG AND HYBRID COMPUTING Substituting this in equation (2.1) gives (2.4) By bringing all the terms in e 0 to the left-hand side, we get e [wA{k + i + -+ {)] ■ -&Λ + · + ] (2.5) from which we obtain the expression x r i 1 I 1 / R 0 R 0 R 0 (2.6) If k is large, the term in equation (2.6) tends to zero and can be neglected. This results in an expression «°--[|'·+|^··· + £°<·] <> which is dependent only on the input voltages e l9 e 2 , .-,e n and the values of the resistors R l9 R 2 , ..., R n . From this expression we see that with an amplifier set up as in Fig. 2.2, we can carry out the operations of summation, multiplication by a constant, and sign inversion. Generally in commercial computers the amplifiers which are assigned for summation will have two values of resistors associated with them, 100 kQ and 1 in 100 V computers, and 10 kQ and 100 kQ in 10 V computers. These are arranged as shown in

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Op Amps: Design, Application, and Troubleshooting

  • David Terrell(Author)
  • 1996(Publication Date)
  • Newnes

    (Publisher)

  Figure 2.25 .

  FIGURE 2.25 The summing network shown in Figure 2.23 can be replaced by its Thevenin equivalent for analysis purposes.

  We can now complete our analysis of the simplified circuit by applying techniques presented for the basic noninverting amplifier.

  Voltage Gain.

  The voltage gain of the circuit in Figure 2.25 can be computed with the noninverting amplifier gain formula given in Equation (2.28) .

  Output Voltage.

  The output voltage of the circuit in Figure 2.25 can be determined by utilizing the basic gain equation of Equation (2.1) :

  Therefore,

  2.6.3 Practical Design Techniques

  The design of a noninverting Summing Amplifier like that shown in Figure 2.23 is an involved process, and the resulting design is difficult to alter without affecting several parameters. Therefore, many designers who need a noninverting Summing Amplifier utilize an inverting Summing Amplifier followed by a simple inverting amplifier. This arrangement is much simpler to design, easier to modify, and costs little more to build. With this in mind, we will not explore the details for designing the generic noninverting Summing Amplifier. However, we will discuss the design of a special case that uses the same basic circuit when we study adder circuits in Chapter 9 .

  2.7 AC-COUPLED AMPLIFIER

  2.7.1 Operation

  The term AC-coupled

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Operational Amplifiers

  • Jiri Dostal(Author)
  • 2013(Publication Date)
  • Newnes

    (Publisher)

  Parti The Operational Amplifier This page intentionally left blank 1. Basic Concepts 1.1 The Operational Amplifier The operational amplifier is a versatile amplifying device, originally intended for use in analog computers to perform linear mathematical operations. Forty years of development of the operational amplifier's internal circuit design reflects, to a significant extent, the development of electronic components from vacuum tubes to monolithic integrated circuits. An increasing refinement of the operational amplifier's properties has shifted the emphasis of its ap-plications from laboratories to industry. Due to its high performance, ver-satility, and low price, the operational amplifier now dominates the field of analog electronic systems. We generally define the operational amplifier as a direct-coupled amplifier with a high gain and a low level of inherent noise, capable of stable operation in a closed-feedback loop. The exact meaning of these characteristics will be given in Chapters 2 and 11. It should be mentioned here that the term direct-coupled does not imply an upper limitation of the amplifier's frequency re-sponse but, on the contrary, an extension of the operating range to zero frequency, or infinitely long periods. The direction of signal flow from input to output in an operational amplifier is given by the triangular shape of its symbol in Figure 1-la. Three of the four illustrated terminals represent the three signal terminals of an actual operational amplifier. These are the inverting input, noninverting input, and output. The fourth signal terminal, the ground, may be either actual (Figure 1—lb) or only virtual (power supply common in Figure 1-lc). In either case, it represents symbolically a group of at least two terminals intended for the supply of energy.

  Sign up to read

  Learn more about book