An NPN transistor is formed by sandwiching a thin layer of P-type material between two layers of N-type material. Transistors may be PNP or NPN transistors.Ī PNP transistor is formed by sandwiching a thin layer of N-type material between two layers of P-type material. Transistors are bipolar devices.Ī bipolar device is a device in which both holes and electrons are used as internal carriers for maintaining current flow. A transistor is a three-terminal device that controls the current through the device depending on the amount of voltage applied to the base. Transistors may be used as AC amplification devices. In each case, the output is merely being compared to the input. Therefore, the term gain is used to describe current gain, voltage gain, and power gain. Note: Gain is a ratio of output to input and has no unit of measure, such as volts or amps, attached to it. Adding amplifiers to obtain the required gain if a single amplifier does not provide enough gain to increase the output signal to the amplitude needed. For many amplifiers, the gain is in the hundreds or even thousands.įigure 1. If the gains of the amplifiers were 8 and 9, respectively, the total gain would be 72 (8 × 9 = 72).Īmplifiers connected in this manner are called cascaded amplifiers. The total gain of the two amplifiers is 100 (10 × 10 = 100). See Figure 1.įor example, amplifier A has a gain of 10 and amplifier B has a gain of 10. In such a case, two or more amplifiers can be used to obtain the gain required. Often, a single amplifier does not provide enough gain to increase the output signal to the amplitude needed. Mathematically, the gain can be found by dividing output by input: A signal applied to the input of the black box results in an output from the box. In determining gain, the amplifier can be thought of as a black box. Gain is a ratio of the amplitude of an output signal to the amplitude of an input signal. The primary objective of an amplifier is to produce gain. Current and resistance are produced by input sensors. Amplifiers are essential for increasing the effect of a small change in voltage. Amplification is accomplished by using a small input signal to control the energy output from a larger source such as a power supply.Īmplification is accomplished by transistors and operational amplifiers (op-amps).
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