differential amplifier


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differential amplifier

[‚dif·ə′ren·chəl ′am·plə‚fī·ər]
(electronics)
An amplifier whose output is proportional to the difference between the voltages applied to its two inputs. Also called difference amplifier.

Differential amplifier

An electronic circuit that is designed to amplify the difference between two voltages measured with respect to a common reference, usually designated as ground. By convention, the net difference of two voltages measured with respect to a common reference is called the differential-mode voltage, while the sum of the voltages, usually divided by two to give an average value, is called the common-mode voltage.

An ideal differential amplifier thus has exactly the same gain from each input to its output, and the amplifier produces an output that is directly proportional to its differential-mode voltage. The amplifier delivers zero output in response to common-mode voltages. If these gains are not exactly equal, then equal (common-mode) voltages applied at each input terminal will not be equal at the amplifier output and their difference will not cancel completely. The common-mode gain, the ratio of the output response of a real differential amplifier to the input signal applied equally to each input terminal, is a measure of this gain mismatch.

Differential amplification is very useful when the signal to be amplified exists in an electrically noisy environment, since the noise voltage is usually a common component of both input voltages and, hence, will cancel when the difference of the amplifier inputs is taken. See Amplifier

For a physical differential amplifier to work properly, the electrical paths of each input signal through the amplifier must be nearly identical. Thus, the most important requirement for a differential amplifier is that it be constructed with transistors with closely matched electrical characteristics. Integrated circuits with amplifier transistors physically close to each other meet the required close matching requirement and are ideally suited for the production of differential amplifiers. See Integrated circuits

Differential-amplifier circuits that are suitable for integrated-circuit fabrication can use either metal oxide semiconductor field-effect transistors (MOSFETs) or bipolar junction transistors (BJTs). The input transistor pair must be matched closely. For best performance, the two load transistors also should be matched. See Transistor

differential amplifier

An electronic circuit that amplifies the difference between two voltages. With one regular input and one inverting input (+ becomes -, - becomes +), it multiplies the difference by a constant factor. Differential amplifiers are used in myriad applications, including microphones, simulation, analog-to-digital conversion and automatic gain control. See op amp.
References in periodicals archive ?
The ADL5566 differential amplifier can be easily designed with the AD9467 data converter, AD9250 and AD9643 dual-channel data converters, ADL5812 RF mixer, ADL5380 RF demodulator and ADF4351 PLL synthesizer for a complete dual-channel receiver design.
DALLAS, July 18, 2013 /PRNewswire/ -- Texas Instruments (TI)(NASDAQ: TXN) today expanded its high-speed amplifier portfolio with two new differential amplifiers that offer the industry's best power-to-performance ratio.
ADI), a world leader in high-performance signal processing and leading provider of amplifier and data conversion technologies, introduced today the industry's first 5-GHz differential amplifier able to drive ADC (analog-to-digital converter) signals from DC to 1 GHz at half the power of competing products.
5-GHz dual differential amplifier is optimized for IF and dc applications and provides a gain of 16 dB.
Pricing and delivery for a 3-Channel Model 121 DC Differential Amplifier is available by contacting t&m@meas-spec.
This enabled us to design the right device for the market and we are now delighted to deliver on our commitment to provide the high performance GX3240 differential amplifier in volume for our customers' 40G RZDQPSK platforms.
Measuring only 2 mm x 2 mm, it is the industry's smallest, high-speed, fully differential amplifier, making it suitable for use in high-density applications.
To form a complete signal path solution, the ADC12Dxx00RF ADC can be teamed with one of National's dual-channel, digitally-controlled variable gain amplifiers (DVGA) or the LMH6554 fully differential amplifier, and LMX2541 frequency synthesizer or one of National's LMK04800 clock jitter cleaners.
The NBK/214 Advanced Neurobiology Teach Kit includes the iWorx 214 Four Channel Computer Interface, LabScribe2 Data Acquisition and Analysis Software, Extracellular Differential Amplifier with Headstage, Intracellular Electrometer, Nerve Bath Chamber, accessories, and courseware, in either PDF, HTML, and hard copy formats.
The ADC16DV160 can be teamed with the dual-channel LMH6517 digitally-controlled variable gain amplifier (DVGA) or the LMH6554 fully differential amplifier.

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