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Special circuits: Integrator and differentiators
Therefore,
These circuits are useful for automobile ignition and fuel injection
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Op-Amp Imperfections in the linear range of operations
• Non-ideal properties in the linear range of operation
• Nonlinear characteristics
• DC offsets
Input and Output Impedances
 An Ideal op amp has infinite input impedance and zero output impedance
 A Real op amp has finite input impedance and nonzero output impedance
 For IC op amps made of BJTs open-loop input impedance is about 1 MW
 For IC op amps made of JFETs open-loop input impedance is about 1012 W
 Open loop output impedance is between 1 and 100 W
 Closed loop impedances will be different, and can be chosen by proper resistors
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Characteristics of two popular Op Amps
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Op-Amp Imperfections in The Linear Range of Operations
Gain and Bandwidth Limitations
 Ideal op amps have infinite open-loop gain magnitude (AoL is infinite), but the gain of a
real op amp is finite and a function of frequency
 dc open-circuit differential voltage gain is typically between 104 to 106
 The bandwidth is usually limited by the designer to prevent oscillations from feedback, by
a process is called frequency compensation
The open loop gain function
of an op-amp usually has a
single dominant pole and is
given as:
 AOL (f)
 A0OL
 fBOL
 AOL (f)
- open-loop gain as function of frequency
- dc open-loop gain
- open-loop break frequency
- constant up to fBOL then it rolls off at 20
dB/decade
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