Tag: Free Book on Semiconductors

  • 8.12 Positive Feedback

    As we’ve seen, negative feedback is an incredibly useful principle when applied to operational amplifiers. It is what allows us to create all these practical circuits, being able to precisely set gains, rates, and other significant parameters with just a few changes of resistor values. Negative feedback makes all these circuits stable and self-correcting. The…

  • 8.11 Differentiator and Integrator Circuits

    By introducing electrical reactance into the feedback loops of an op-amp circuit, we can cause the output to respond to changes in the input voltage over time. Drawing their names from their respective calculus functions, the integrator produces a voltage output proportional to the product (multiplication) of the input voltage and time; and the differentiator…

  • 8.10 The Instrumentation Amplifier

    What Is an Instrumentation Amplifier? An instrumentation amplifier allows an engineer to adjust the gain of an amplifier circuit without having to change more than one resistor value. Compare this to the differential amplifier, which we covered previously, which requires the adjustment of multiple resistor values. The so-called instrumentation amplifier builds on the last version…

  • 8.9 Building a Differential Amplifier

    Differential Op-Amp Circuits An op-amp with no feedback is already a differential amplifier, amplifying the voltage difference between the two inputs. However, its gain cannot be controlled, and it is generally too high to be of any practical use. So far, our application of negative feedback to op-amps has resulting in the practical loss of…

  • 8.8 Averager and Summer Circuits

    If we take three equal resistors and connect one end of each to a common point, then apply three input voltages (one to each of the resistors’ free ends), the voltage seen at the common point will be the mathematical average of the three. This circuit is really nothing more than a practical application of…

  • 8.7 Voltage-to-Current Signal Conversion

    In instrumentation circuitry, DC signals are often used as analog representations of physical measurements such as temperature, pressure, flow, weight, and motion. Most commonly, DC current signals are used in preference to DC voltage signals, because current signals are exactly equal in magnitude throughout the series circuit loop carrying current from the source (measuring device)…

  • 8.6 An Analogy for Divided Feedback

    A helpful analogy for understanding divided feedback amplifier circuits is that of a mechanical lever, with relative motion of the lever’s ends representing change in input and output voltages, and the fulcrum (pivot point) representing the location of the ground point, real or virtual. Take for example the following noninverting op-amp circuit. We know from…

  • 8.5 Divided Feedback

    If we add a voltage divider to the negative feedback wiring so that only a fraction of the output voltage is fed back to the inverting input instead of the full amount, the output voltage will be a multiple of the input voltage (please bear in mind that the power supply connections to the op-amp…

  • 8.4 Negative Feedback

    If we connect the output of an op-amp to its inverting input and apply a voltage signal to the noninverting input, we find that the output voltage of the op-amp closely follows that input voltage (I’ve neglected to draw in the power supply, +V/-V wires, and ground symbol for simplicity): As Vin increases, Vout will…

  • 8.3 The Operational Amplifier

    Long before the advent of digital electronic technology, computers were built to electronically perform calculations by employing voltages and currents to represent numerical quantities. This was especially useful for the simulation of physical processes. A variable voltage, for instance, might represent velocity or force in a physical system. Through the use of resistive voltage dividers…

  • 8.2 Single-ended and Differential Amplifiers

    For ease of drawing complex circuit diagrams, electronic amplifiers are often symbolized by a simple triangle shape, where the internal components are not individually represented. This symbology is very handy for cases where an amplifier’s construction is irrelevant to the greater function of the overall circuit, and it is worthy of familiarization: The +V and…

  • 8.1 Introduction to Operational Amplifiers (Op-amps)

    What is an Operational Amplifier (Op-amp)? Operational Amplifiers, also known as Op-amps, are basically a voltage amplifying device designed to be used with components like capacitors and resistors, between its in/out terminals. They are essentially a core part of analog devices. Feedback components like these are used to determine the operation of the amplifier. The…

  • 7.10 Field-effect-controlled Thyristors

    Two relatively recent technologies designed to reduce the “driving” (gate trigger current) requirements of classic thyristor devices are the MOS-gated thyristor and the MOS Controlled Thyristor, or MCT. MOS-gated Thyristor The MOS-gated thyristor uses a MOSFET to initiate conduction through the upper (PNP) transistor of a standard thyristor structure, thus triggering the device. Since a…

  • 7.9 The Silicon-Controlled Switch (SCS)

    If we take the equivalent circuit of an SCR and add another external terminal, connected to the base of the top transistor and the collector of the bottom transistor, we have a device known as a silicon-controlled-switch, or SCS: (Figure below) The Silicon-Controlled Switch(SCS) This extra terminal allows more control to be exerted over the…

  • 7.8 The Unijunction Transistor (UJT)

    Unijunction transistor: Although a unijunction transistor is not a thyristor, this device can trigger larger thyristors with a pulse at base B1. A unijunction transistor is composed of a bar of N-type silicon having a P-type connection in the middle. See Figure (a). The connections at the ends of the bar are known as bases…