1. Effect of Feedback

Feedback .

. B , B

. , , amp

A .

. + positive feedback, - negative feedback .

( input .) input impedance ,

. B feedback ,

. (input output .) output impedance

.

output impedance 0 .

OP-Amp , B=1 A . , x , 6dB/octave . output inverting input, Ground B=0.01 . A A .

2. Positive Feedback

LF411 Comparator Comparator() , . 311 Comparator 311 OP-amp output npn BJT . Feedback noise

noise ( ) , noise . Op-Amp output 0V +15V 0V transition .

transition . Non-inverting input ground output 300 ground 10 , output 1/30 Non-inverting input . threshold transition 0V . 0V threshold noise threshold .

RC Relaxation Oscillators

DC Oscillator inverting input . Op-Amp output +15V 2 voltage divide 1.5V . ( ) . 1.5V . . 0V . triangle wave .

Negative Impedance Converter(NIC) Negative Impedance Converter . scope . scope A B . scope inductor B 2 .

3. Oscillators

http://pdf1.alldatasheet.com/datasheet-pdf/view/17798/PHILIPS/ICM7555CD.html 555 RC oscillator/timer , . 555 . RC Relaxation Oscillators .Sine oscillator : Wien Bridge

oscillator Wien Bridge . , Negative Feedback, Positive Feedback , Feedback . .

Nasty Oscillator

positive feedback feedback . Golden Rules input X feedback circuit . , out (-) negative feedback . BJT phase 180 (-) (-) (+) positive feedback . out (-) . LPF 90 180 positive feedback .Unstable Amplifier Circuit

. , LPF 3dB 45 . . LPF , positive feedback .

, , phase shift 180 Op-Amp Compensation gain . A B .

A Op-Amp loop gain . Frequency Compensation .

B . Ground .

Oscillations withOUT Op-Amps , Gain 1 feedback oscillation . Miller Effect , Transistor inductor oscillation .

1 : Two Comparators : Op-Amp Comparator IC Comparator

(a) Op-Amp as ComparatorOp-Amp . 100 sine wave .(b) Special-Purpose Comparator IC411 Op-Amp 311 Comparator .(=1)Bottom of the swing ground , 15V .(c) Schmitt Trigger

thresholds .hysteresis , output transition . Comparator . Ground pin 15V .

: (a) square wave (b) square wave transition . (c) (b) transition .

2 : RC Oscillator : RC Relaxation Oscillator

Comparator inverting input RC network . . oscillation . : V+ V- triangle wave .

3 : 7555 IC Oscillator : 7555 IC Oscillator RC Oscillator

555 7555 . 6 7 short .

:

2 .

4 : Sawtooth Oscillator : Sawtooth Oscillator

3 10 2 .Probe 10X .

: .

5 : Triangle Oscillator Transistor 2N3906 JFET 1N5294 .

6 : Sine Wave Oscillator : Wien Bridge : Wien Bridge Sine Wave gain

Wien Bridge . feedback .560 negative feedback . (+) input . scope . : feedback 560 sine .

7 : Follower : Op-Amp

, .emitter , collector .

-Supply Bypass(Shrinking the Disturbance)collector ground collector . 0.01~0.1 .

-Killing High-Frequency GainBase Emitter gain .

: , collector inductor , 2 .

8 : Op-Amp Instability : Phase Shift Oscillation

. . square wave oscillation sine wave ., pot oscillation . divide .

: square, sine wave oscillation , oscillation .