An integrated circuit amplifier is a compactly packaged collection of active and passive devices that may boost the voltage or current level of a signal. The active components are transistors, three-terminal semiconductor devices that are capable of current gain, wherein a small change in current produces a pro-rated change in the integrated circuit amplifier output. Discreet electronic circuits, which use separate transistors, resistors, and capacitors, were the earliest prototype of the integrated circuit. The integrated circuit amplifier or chip amplifier or microchip amplifier was the result of the attempt to reduce the weight and space requirements of fixed and portable electronic gadgets and equipment. There are applications where the matching of transistors was required to produce maximum high-fidelity reproduction of the input signals.
Home computers that have sound cards with integrated circuit amplifiers that amplify sound are very popular in multimedia applications. The integrated circuit amplifier accepts the output from the digital-to-analog converter. This output is fed into another integrated circuit amplifier until the power level is enough to drive a speaker. In the opposite direction, when a microphone is used, the small signal from a microphone is amplified, or boosted, into a level sufficient to be detected by an analog-to-digital converter. This digital representation of the sound or voice can then be transmitted over digital paths using voice over Internet protocol (VOIP) among others.
The integrated circuit amplifier comes with several pins or package terminals. Real-world integrated circuits may also have performance-enhancing features such as dual-power supply input. The input may also be a differential type that has a “–“ or inverting input and a “+” or non-inverting input, which is an operational amplifier (OpAmp) that is used extensively in analog computing devices and feedback control systems that use models of the correction signal. Using resistors and/or capacitors, an OpAmp may be wired to produce a signal that is proportional, integral, or a derivative of the correction signal.
Various electronic devices, such as cell phones, and digital devices, such as computers, use many types of integrated circuit amplifiers. There are even integrated circuit amplifiers that operate in the radio frequency (RF) band besides the audio frequency band. RF amplifier integrated circuits are used in compact receiver applications such as for personal communications equipment like cell phones and personal data assistants. OpAmp integrated circuits usually have eight pins or more. The OpAmp is available in various types depending on the needed performance.
Special features have been added for the integrated circuit amplifier. For battery operation, it may be useful to place an amplifier on standby, thus reducing power consumption in devices such as two-way radios used in rescue operations. Other features include audio noise cancellation that ensures voice messages are easily understood under adverse conditions.