frequency response of amplifier
DESCRIPTION
Frequency Response of Amplifier. Input signal of an amplifier can always be expressed as the sum of sinusoidal signals. The amplifier performance can be characterized by its frequency response. Frequency response of a linear amplifier. Amplifier Transmission or Transfer Function. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/1.jpg)
1
Frequency Response of Amplifier
• Input signal of an amplifier can always be expressed as the sum of sinusoidal signals.
• The amplifier performance can be characterized by its frequency response.
![Page 2: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/2.jpg)
2
Amplifier Transmission or Transfer Function
![Page 3: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/3.jpg)
3
• The figure indicates that the gain is almost constant over a wide range of frequency range ω1 to ω2 .
• The band of frequencies over which the gain of the amplifier is within 3dB is called the amplifier bandwidth.
• The amplifier is always designed so that its bandwidth coincides with spectrum of the input signal (Distortion less amplification)
![Page 4: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/4.jpg)
4
Amplifier Transfer Function• Amplifier Types
– Direct Coupled or dc amplifier– Capacitively Coupled or ac amplifier
• Difference– Gain of the ac amplifier falls off at low frequencies
• Amplifier gain is constant over a wide range of frequencies, called Mid-band
![Page 5: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/5.jpg)
5
• Evaluate the circuit in Frequency Domain by carrying out the circuit analysis in the usual way but with inductance and capacitance represented by their reactances– An inductance L has a reactance or impedance jωL and Capacitance C
has a reactance or impedance 1/jωC
• The circuit analysis to determine the frequency response can be in complex frequency domain by using complex frequency variable ‘s’– An inductance L has a reactance or impedance sL and Capacitance C
has a reactance or impedance 1/sC
![Page 6: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/6.jpg)
Frequency Response of DC Amplifier
Figure 6.12 Frequency response of a direct-coupled (dc) amplifier. Observe that the gain does not fall off at low frequencies, and the midband gain AM extends down to zero frequency.
![Page 7: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/7.jpg)
7
A resistively loaded MOS differential pair
It is assumed that the total impedance between node S and ground is ZSS,
consisting of a resistance RSS in parallel with a capacitance CSS.
CSS includes Cbd & Cgd of QS as well as Csb1 & Csb2.
![Page 8: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/8.jpg)
8
Differential Half-circuit.
Frequency Response: Differential Gain
Frequency Response is the same as studied earlier for common source amplifier.
![Page 9: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/9.jpg)
Microelectronic Circuits - Fifth Edition Sedra/Smith
9
Figure 6.20 High-frequency equivalent-circuit model of the common-source amplifier. For the common-emitter amplifier, the values of Vsig and Rsig are modified to include the effects of rp and rx; Cgs is replaced by Cp, Vgs by Vp, and Cgd by Cm.
![Page 10: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/10.jpg)
Microelectronic Circuits - Fifth Edition Sedra/Smith
10
Figure 6.23 Analysis of the CS high-frequency equivalent circuit.
![Page 11: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/11.jpg)
Microelectronic Circuits - Fifth Edition Sedra/Smith
11
Figure 6.24 The CS circuit at s 5 sZ. The output voltage Vo 5 0, enabling us to determine sZ from a node equation at D.
![Page 12: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/12.jpg)
Quiz # 3 (Syn A)Determine the short circuit transconductance (Gm) of the given circuit.
![Page 13: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/13.jpg)
Quiz # 3 (Syn B)Determine the short circuit transconductance (Gm) of the given circuit.
![Page 14: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/14.jpg)
14
Common-mode half-circuit.
![Page 15: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/15.jpg)
15
Common-mode half-circuit.
D
D
SS
Dcm R
RRRA
2
SSSSD
D
SS
D
D
D
SS
Dcm RsC
RR
RR
RR
ZRA
1
22
SSSS
SSSSSSSS RsC
RCRZ1
||
Acm has a zero on the negative real-axis of the s-plan with frequency ωz
SSSSz
SSSSz CR
fCR p
2
11
![Page 16: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/16.jpg)
16
Figure 7.37 Variation of (a) common-mode gain, (b) differential gain, and (c) common-mode rejection ratio with frequency.
SSSSSS
D
SS
Dcm RsC
RR
ZRA 1
22
![Page 17: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/17.jpg)
17
Figure 7.37 Variation of (a) common-mode gain, (b) differential gain, and (c) common-mode rejection ratio with frequency.
SSSSSS
D
SS
Dcm RsC
RR
ZRA 1
22
![Page 18: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/18.jpg)
18
Figure 7.38 The second stage in a differential amplifier is relied on to suppress high-frequency noise injected by the power supply of the first stage, and therefore
must maintain a high CMRR at higher frequencies.
![Page 19: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/19.jpg)
Exercise 7.15
![Page 20: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/20.jpg)
Microelectronic Circuits - Fifth Edition Sedra/Smith
20
Figure 6.22 Application of the open-circuit time-constants method to the CS equivalent circuit of Fig. 6.20.
![Page 21: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/21.jpg)
21
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier.
43311 gsgsdbdbgdm CCCCCC
xdbgbdbgdL CCCCCC 3422
![Page 22: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/22.jpg)
22
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier.
43311 gsgsdbdbgdm CCCCCC xdbgbdbgdL CCCCCC 3422
![Page 23: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/23.jpg)
23
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier.
mm
idm
g sCg
vgV
33
2
3
3
4344
1
22
m
m
idm
mm
idmm
gmd
gCs
vg
sCg
vggVgI
21
2
3
240id
m
m
m
idm
ddvg
gCs
vgIII
Lo
o
Lout
Lout CsR
RsC
RRsC
rrR
1
1||1|||| 00402
Lo
m
m
idom CsR
gCs
vRgV
11
1
12
3
0
3
3
1
21
11
m
m
m
m
Loomd
gCs
gCs
CsRRgA
![Page 24: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/24.jpg)
25
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier. (b) The overall transconductance Gm as a function of frequency.
xdbgbdbgdL CCCCCC 3422
0201 & rrNeglect
mm
idm
g sCg
vgV
33
2
3
3
4344
1
22
m
m
idm
mm
idmm
gmd
gCs
vg
sCg
vggVgI
21
2
3
2440id
m
m
m
idm
ddvg
gCs
vgIII
43311 gsgsdbdbgdm CCCCCC
![Page 25: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/25.jpg)
26
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier. (b) The overall transconductance Gm as a function of frequency.
Lo
o
Lout
Lout CsR
RsC
RRsC
rrR
1
1||1|||| 00402
21
2
3
0id
m
m
m
idm vg
gCs
vgI
Lo
m
m
idom CsR
gCs
vRgV
11
1
12
3
0
3
3
1
21
11
m
m
m
m
Loomd
gCs
gCs
CsRRgA
![Page 26: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/26.jpg)
27
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier. (b) The overall transconductance Gm as a function of frequency.
3
3
1
21
11
m
m
m
m
Loomd
gCs
gCs
CsRRgA
L1 C of valuelarge todue poleDominanat 2
1
Lop CRf
p
omRgGainMidband
m
mp C
gfp2
32
m
mz C
gfp2
2 3
The zero frequency (fz) is twice that of the pole (fp2)
![Page 27: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/27.jpg)
28
Figure 7.39 (a) Frequency-response analysis of the active-loaded MOS differential amplifier. (b) The overall transconductance Gm as a function of frequency.
Lop CRf
p21
1
omRgGainMidband
m
mp C
gfp2
32
m
mz C
gfp2
2 3
![Page 28: Frequency Response of Amplifier](https://reader036.vdocuments.net/reader036/viewer/2022062410/56816047550346895dcf6ad7/html5/thumbnails/28.jpg)
Assignment # 4
• Carry out detailed frequency response analysis of the current-mirror-loaded MOS differential pair circuit.
• Due date: 2 Dec 2011