chapter 6 - Analog IC Design.org

Chapter 6 – Section 1 (5/2/04) Page 6.1-6
Linear and Dynamic Characteristics of the Op Amp
Differential and common-mode frequency response:
⎛V ⎜ 1 (s)+V 2 (s)⎞
⎟
V out (s) = A v (s)[V 1 (s) - V 2 (s)] ± A c (s) ⎜
⎟
⎝ 2 ⎠
Differential-frequency response:
A v0
A v0 p 1 p 2 p 3···
A v (s) =
⎛ s ⎞⎛
s ⎞⎛
s ⎞
= (s -p
⎜ ⎟⎜
⎟⎜
⎟ 1 )(s -p 2 )(s -p 3 )···
⎜ ⎟
⎝p 1
- 1 ⎜ ⎟
⎠⎝p 2
- 1 ⎜ ⎟
⎠⎝p 3
- 1 ···
⎠
where p 1 , p 2 , p 3 ,··· are the poles of the differential-frequency response (ignoring zeros).
20log10(A v0 )
|A v (jω)| dB
Asymptotic
Magnitude
Actual
Magnitude
-6dB/oct.
GB
0dB
Fig. 110-06
ω 1
ω 2 ω 3
ω
-12dB/oct.
-18dB/oct.
CMOS Analog Circuit Design © P.E. Allen - 2004
Chapter 6 – Section 1 (5/2/04) Page 6.1-7
Other Characteristics of the Op Amp
Power supply rejection ratio (PSRR):
PSRR ∆V DD
= ∆V OUT
A v (s) V o/V in (V dd = 0)
= V o /V dd (V in = 0)
Input common mode range (ICMR):
ICMR = the voltage range over which the input common-mode signal can vary
without influence the differential performance
Slew rate (SR):
SR = output voltage rate limit of the op amp
Settling time (T s ):
-
+
v OUT
Final Value + ε
Final Value
Final Value - ε
v OUT (t)
ε
ε
Upper Tolerance
Lower Tolerance
Settling Time
0
0
v IN
Fig. 110-07
T s
t
CMOS Analog Circuit Design © P.E. Allen - 2004