opamp1 - ELEC 101 1 Op Amp Circuits 1 2009/10 Spring...

ELEC 101 Op Amp Circuits 1 2009/10 Spring
Voltage Amplifier
also called
Voltage-Controlled Voltage-
Amplifier
or
V-to-V converter
1
R
i
: input resistance
Circuit Model of voltage amplifier
A
V
V
i
R
i
R
O
R
O
: output resistance
A
V
: voltage gain
V
i
: input voltage
V
O
: output voltage
a
V
O
V
i
Example: HiFi pre-amp

ELEC 101 Op Amp Circuits 2 2009/10 Spring
A
V
V
i
R
L
R
S
R
O
load
V
S
Circuit Model of source – voltage amplifier – load
amplifier
source
R
S
:
source resistance
R
L
:
load resistance
For
ideal voltage amplifier
,
R
i
= 
( R
i
>> R
S
)
R
O
= 0
( R
O
<< R
L
)
R
i
b
c
S V O
V A V 

0
A
V
V
i
R
i
R
O
V
i
V
O
V
O
V
i
V
S
:
source voltage
Proof
S i
S i
V V
R R


S V
i V O
O L
V A
V A V
R R



d
With
R
i
= 
With
R
O
= 0

ELEC 101 Op Amp Circuits 3 2009/10 Spring
Example
Temperature
sensor
Voltage
amplifier
Meter
display
V
S
= 0V at 0  C
+1mV/  C
R
S
= 300 
R
i
= 2k 
R
O
= 400 
R
L
= 10k 
V
O
+
-
+
-
V
i
0V 1V
0  C
100  C
Find voltage gain A
V
of the voltage amplifier.
Need to have V
O
= 1V when V
S
= 100mV (at 100  C)