Frequency response of amplifiers, Electrical Engineering

Assignment Help:

Q. Frequency response of amplifiers?

All amplifiers exhibit variations of performance as the signal frequency is changed. The frequency response of an amplifier may be defined as the functional dependence of output amplitude and phase upon frequency, for all frequencies. Invariably there is a maximum frequency above which amplification does not occur. Depending on the design of the circuit, there may also be a lower frequency limit below which amplification disappears. The range of frequencies over which significant amplification of themagnitude is obtained is known as the passband, which is bounded by the upper cutoff frequency and the lower cutoff frequency (if one exists).Dc-coupled amplifiers, in which the stages are coupled together for all frequencies down to zero, have no low-frequency limit. On the other hand, circuits containing coupling capacitors that couple stages together for ac while isolating them for dc are limited in their low-frequency response. The high-frequency deterioration of the voltage gain is due to the effect of capacitances that are internal to the transistor.

786_Frequency response of amplifiers.png

Figure shows a typical frequency response of a voltage amplifier.While most often the magnitude of the gain is discussed (because it defines the frequency range of useful gain), the phase response becomes important for transient calculations. The midband region is the range of frequencies where gain is nearly constant. Amplifiers are normally considered to operate in this useful midband region. The bandwidth of an amplifier is customarily defined as the band between two frequencies, denoted by ωH and ωL, which corresponds to the gain falling to 3 dB below the midband constant gain. Thus,

W3dB = ωH - ωL

which is shown in Figure. When both ωL and ωH have significant values, the amplifier is known as a bandpass amplifier. A narrow-bandpass amplifier is one in which W3dB is small relative to the center frequency of the midband region. In a low-pass unit (dc amplifier) there is no low 3-dB frequency.


Related Discussions:- Frequency response of amplifiers

Write short note on common vs associated channel signalling, Q. Write short...

Q. Write short note on Common vs. associated channel signalling. Associated vs. Common channel signalling: Out band signalling suffers from very limited bandwidth. Both a

When both mt2 and gate are positive, When both  MT 2 and  Gate  are pos...

When both  MT 2 and  Gate  are positive In this  junction  P 1 N 1   and P 2 N 2   are forward  biased whereas junction N 1 P 2 is reverse biased. The gate current flows  thr

Description of capacitor, Description of Capacitor r A capacitor has cap...

Description of Capacitor r A capacitor has capacitance of one Farad when current charging of one Ampere flows in one second. This process causing a transferring of one volt in p

Determine the minimum number of poles for the motor, Q. From a three-phase,...

Q. From a three-phase, 60-Hz system, through a motor-generator set consisting of two directly coupled synchronous machines, electric power is supplied to a three-phase, 50-Hz syste

Determine the output waveform of the voltage, Q. The first four harmonics i...

Q. The first four harmonics in the Fourier series of current waveform given by where I m = 15 mA and T = 1 ms. If such a current is applied to a parallel combination of R

D.c machine, What are the advantages of distributing windings in an alterna...

What are the advantages of distributing windings in an alternator?

Conducting material, #question.classification of conducting material.

#question.classification of conducting material.

Determine the dielectric constant of air in practically, The dielectric con...

The dielectric constant of air is practically taken as (A) more than unity.                         (B) Unity.  (C) less than unity.                           (D) Zero.

Types of bias circuit for class a amplifiers, Types of bias circuit for Cla...

Types of bias circuit for Class A amplifiers: There are five common types of biasing circuits used with Class A bipolar transistor amplifiers: A. Fixed bias B. Collector

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd