23-12-2010, 11:47 AM
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Function of Amplifiers
Amplifiers provides
GAIN
Filtering, Signal processing, Correction for Nonlinearities
Ideal OP Amps
Transfer Function = Output / Input
Voltage Amp TF (Gain):
Usually Av 1
OP Amp is preferred
Easy to use in circuit designed compared to discrete Transistor circuits
Ideal OP Amps (Cont.)
Assumptions
Open loop Gain = Infinity
Input Impedance Rd = Infinity
Output Impedance Ro = 0
Bandwidth = Infinity
Infinite Frequency Response
vo=0 when v1 = v2
No Offset Voltage
Ideal OP Amps (Cont.)
Note
v0 = A(v2 – v1)
If v0 = , A = (Typically 100,000)
Then v2 – v1 = 0 v2 = v1
Since v2 = v1 and Rd =
We can neglect the current in Rd
Rule 1
When the OP Amp is in linear range the two inputs are at the same voltage
Rule 2
No Current flows into either terminal of the OP Amp
Basic OP Amp Circuit Blocks
Inverting Amplifier
Noninverting Amplifier
Unity-Gain Amplifier
Differential Amplifier
Instrumental Amplifier
The Electrocardiogram Amplifier