Electronics - Revision 2. In electronics, it is the voltage that is important. Draw voltage time...
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Electronics - Revision 2. In electronics, it is the voltage that is important. Draw voltage time graphs for analogue and digital systems. 3. Draw a block diagram for a public address system. 4. Why do we need an amplifier in the system ? 5. What is the voltage gain of an amplifier ? 6. What is the gain of an amplifier which has input voltage of 2V and output voltage of 8V ? 7. What does an amplifier do to the frequency of the signal ? 1. Copy and complete the three blocks which make up an electronic system. Tutorial Questions page 72 Qu 1 to 6
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Transcript of Electronics - Revision 2. In electronics, it is the voltage that is important. Draw voltage time...
Electronics - Revision
2. In electronics, it is the voltage that is important. Draw voltage time graphs for analogue and digital systems.3. Draw a block diagram for a public address system.4. Why do we need an amplifier in the system ?5. What is the voltage gain of an amplifier ?6. What is the gain of an amplifier which has input voltage of 2V and output voltage of 8V ?7. What does an amplifier do to the frequency of the signal ?
1. Copy and complete the three blocks which make up an electronic system.
Tutorial Questions page 72 Qu 1 to 6
Operational amplifiers (op amps) are multistage amplifiers and can give high gain with very little distortion. Fortunately we don’t have to know how they operate – just how they can be used.
_
+
Inverting input
Non-inverting inputoutput
Circuit symbol
Connecting the power supply
2 x 9V
batteries
Vout
Adjust the offset control until Vout = 0 this balances the batteries
The Op Amp
– Inverting Mode, d.c.
VoV1
-
+
Rf
R1
V1 Vo
0V
+Vsupply
Feedback resistor
The Op Amp
– Inverting Mode, d.c.
R1() Rf () V1(V) VO(V) Vgain Rf/R1
100k 100k 0.5
10k 100k 0.5
100k 10k 0.5
100k 1M 0.5
1M 100k 0.5
10k 1M 0.5
VoV1
Op Amp in inverting mode
Vo = - Rf V1
R1
Tutorial Questions page 74 Qu 9
Revision Ex 5.1
Uses of an op amp in inverting mode
Inverting (changing +/-)
Multiplication (amplifying)
Addition
Binary/digital converter
Making square waves
Try the experiments showing these.
Tutorial question p73 Qu 8, 10 to15
Revision Ex 5.2 and 5.3
Op Amp Differential Mode
R2
R1 Rf
V
out
-
+
Rf
R1
V1 VoR3
R2V2
+Vsupply
+Vsupply
R1 = R2 = R3 = Rf = 10k
V1 V2 Vo
0.6 0.4
1.0 0.4
0.3 1.0
0.6 1.0
1.8 0.6
- 0.2
-0.6
0.7
0.4
-1.2
Vo = V2 – V1
R1 = R2 = 10k Rf = R3 = 100k
V1 V2 Vo
1.0 1.1
2.0 2.2
0.6 0.8
0.7 0.5
Op amp in the differential mode.
Vo = (V2 – V1) Rf
R1
The op amp finds the difference between the two inputs ie subtracts them. It then amplifies this difference.
Tutorial questions p 76 Qus 16 to 21
Rev Qus Ex 5.4 and 5.6
For higher Rf R3
R1 R2
NPN transistor PNP Transistor
b
+0.7 Ve at 0V
c connected to +Vs b
- 0.7V
c connected to - Vs
e at 0V
b base
c collector
e emmitter
I I
