1 1.6 op-amp basics basic op-amp op-amp equivalent circuit practical (r i = high, r o = small)ideal...
TRANSCRIPT
1
1.6 Op-Amp Basics
Basic Op-Amp
Op-amp equivalent circuit
Practical (Ri = high , Ro = small) Ideal (Ri =∞ , Ro = 0)
2
1.6 Op-Amp Basics
Basic Operation of Op-Amp input voltage at minus (-) output voltage opposite in phase input voltage at plus (+) output voltage in phase
Basic Op-Amp - Constant-gain multiplier
Input signal is applied through resistor Ri to the minus input
Output is connected to the same minus input through resistor Rf
Resulting output: opposite in phase to input signalInverting constant gain multiplier
3
1.6 Op-Amp Basics
Op-amp ac equivalent circuit
Basic Op-Amp - Constant-gain multiplier
4
1.6 Op-Amp Basics
Ideal Op-amp equivalent circuit Redrawn equivalent circuit
(for circuit analysis)
Basic Op-Amp - Constant-gain multiplier
5
1.6 Op-Amp Basics
11
1 VRR
RV
f
fi
Using Superposition theorem
Basic Op-Amp - Constant-gain multiplier
i) V1 only (set –AvVi =0)
ii) –AvVi only (set V1 =0)
ivf
i VARR
RV
1
12
6
1.6 Op-Amp Basics
11
VRA
RV
v
fi
11)1(V
RAR
RV
vf
fi
Basic Op-Amp - Constant-gain multiplier
ivff
fiii VA
RR
RV
RR
RVVV
1
11
121
i
f
v
f
i
v
i
iv
i
o
V
V
R
R
RA
VR
V
A
V
VA
V
V 1
11
1
11 R
R
V
V fo
It is shown that the ratio i/o depends only on the value of Rf and R1
7
1.6 Op-Amp Basics
Basic Op-Amp - Unity Gain
111
R
R
V
V foIf Rf = R1
Gain with negative sign shows that the output voltage has undergone 180º phase inversion from input signal
Basic Op-Amp - Constant Gain
If Rf = 10R1 1011
R
R
V
V fo
If we select precise values for Rf and Ri, we can obtain a wide range of gains
Gain accuracy depends on resistors used
Gain is slightly affected by temperature & other circuit factors
8
1.7 Practical Op Amp Circuits
Inverting Amplifier Non-inverting Amplifier
11
0 1R
R
V
V f11
0
R
R
V
V f
Inverting constant gain multiplier Non-inverting constant gain multiplier
9
1.7 Practical Op Amp Circuits
Non-inverting Amplifier
01
11 V
RR
RV
f
Equivalent circuit Non-inverting constant-gain multiplier
11
1
1
0 1R
R
R
RR
V
V ff
Which results in;Since Vi = 0, using voltage divider rule,
10
1.8 Data Sheet LM741
11
1.8 Data Sheet LM741
ABSOLUTE MAXIMUM RATINGS
Supply voltage = +22V
Internal power dissipation = 500mW
Differential input voltage = + 30V
Input voltage = + 15V
ELECTRICAL CHARACTERISTICS
Input offset voltage
Input offset current
Input bias current
Input resistance
12
1.8 Data Sheet LM741
ELECTRICAL CHARACTERISTICS
Large signal voltage gain
Output voltage swing
Output short circuit current
Supply voltage rejection ratio
Bandwidth
Slew rate
Supply current
Power consumption
13
1.8 Data Sheet LM741
14
1.8 Data Sheet LM741
15
1.8 Data Sheet LM741