Download Integrated Circuit (IC) or Operational Amplifier (Op

For Third year Biophysics Special Students.
Prepared by:
Abdo A. Elfiky.
Assistant Lecturer, Biophysics Department,
Faculty of Science,
Cairo University.
Introduction
 Integrated circuit (IC),
Microcircuit, Microchip,
Silicon chip, or Chip) is a small
electronic device made out of a
semiconductor material. The
first integrated circuit was
developed in the 1950s.
 There are two main advantages
of ICs over discrete circuits: cost
and performance.

741 type op-amp (1968)
IC 741 Biophysics department
Op-Amp positioning on the board
IC 741 Biophysics department
Operational amplifier
 Op-amps were used to perform
mathematical operations such as
addition, subtraction,
integration,and differentiation,
hence the term operational.
 The op-amp has two input
terminals, called the inverting
input (-) and the non-inverting
input (+), and one output
terminal.
IDEAL OP-AMP
Open-Loop Voltage Gain Aol
100,000 volts
1 volt
1 volt
Closed-Loop Voltage Gain Acl
 Op-amp can be connected using negative feedback to
stabilize the gain and increase frequency response.
 Negative feedback takes a portion of the output and
applies it back out of phase with the input, creating an
effective reduction in gain. This closed-loop gain is
usually much less than the
open-loop gain and
independent of it.
Voltage Follower
 Used as a buffer amplifier to eliminate loading effects
or to interface impedances (connecting a device with a
high source impedance to a device with a low input
impedance)
-99,999 V
100,000 volts
1 volt
Voltage Follower
Non-Inverting Amplifier
 In a non-inverting op-amp, the input signal is applied
to the non-inverting input (+). The output is applied
back to the inverting input (-) through the feedback
network formed by Ri and Rf .
- 49,999 V
100,000 volts
If Rf = Ri = 1KΩ,
Then Vf = ½ Vout
1 volt
Acl = 100,000 / 49,999 = ~ 2
Inverting Amplifier
 In an inverting op-amp, the input signal is applied
through a series of input resistor Ri to the inverting
input. Also, the output is feedback through Rf to the
same input, The non-inverting input is grounded.
- 50,001 V
100,000 volts
If Rf = Ri = 1KΩ,
Then Vf = ½ Vout
1 volt
Acl = 100,000 / 50,001 = ~ 2
Procedure:Non-inverting connection:
1. Connect the circuit of the non-inverting op-amp. [ Ri
(constant) = 1000 ; Rf (variable) = 0.5K, 1k, 2k,
3k, 5.5k, 8K and 10k)].
2. For each value of the Rf find the closed loop gain Acl
experimentally (Vout/Vin), and theoretically
((Rf+Ri)/Ri).
3. Draw a relation between Acl and the values of Rf
experimental and theoretical.
Non-inverting op-amp
Rf (*10+3
ohm)
Vin (volts) Vout (volts)
Acl (exp.)
Acl (theo.)
0.5
2
3.9
1.95
1.5
1
2
3.8
1.9
2
2
2
5.4
2.7
3
3
2
7.1
3.55
4
5.5
2
11.6
5.8
6.5
8
1
7.6
7.6
9
9.8
1
9
9
10.8
Non-inverting op-amp
12
10
Acl
8
6
4
2
0
0
2
4
6
Rf*10+3
8
10
12
Procedure:Inverting connection:
1. Connect the circuit of the Inverting op-amp. [ Ri
(constant) = 1000 ; Rf (variable) = 0.5K, 1k, 2k,
3k, 5.5k, 8K and 10k)].
2. For each value of the Rf find the closed loop gain Acl
experimentally (Vout/Vin), and theoretically (–Rf/Ri).
3. Draw a relation between Acl (experimental and
theoretical) and the values of Rf.
Inverting op-amp
Rf (*10+3 ohm)
Vin (volts)
Vout (volts)
Acl (exp.)
Acl (theo.)
0.5
2
1
0.5
0.5
1
2
2
1
1
2
2
4.6
2.3
2
3
2
5.3
2.65
3
5.5
1
4.8
4.8
5.5
8
1
6.8
6.8
8
9.75
1
8.4
8.4
9.75
Inverting op-amp
12
10
Acl
8
6
4
2
0
0
2
4
6
Rf*10+3
8
10
12
Summing Amplifier
Procedure:Connect the circuit of the Inverting op-amp. [ Rin1
,Rin2 are constant = 1000 ; Rf (variable) = 1k, 2k,
3k, 5.5k, and 8K ].
2. For each value of the Rf find the output voltage Vout
experimentally, and theoretically (–Rf/R(Vin1+Vin2)).
3. Draw a relation between Vout (experimental and
theoretical) and the values of Rf.
1.
Summing Amplifier
Rf (*10+3 ohm)
Vin1
Vin2
Vout (exp.)
Vout (theo.)
0.994
0.5
0.5
0.82
0.994
2.07
0.5
0.5
2
2.07
3.005
0.5
0.5
3
3.005
5.9
0.5
0.5
6
5.9
8.02
0.5
0.5
7.6
8.02
Summing Amplifier
9
8
7
Vout
6
5
4
3
2
1
0
0
2
4
6
Rf *10+3
8
10
Thank you
11/5/2008
prepared by: Abdo A. Elfiky
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