Lecture 14

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EE 359 Electronic Circuits

Filters and Tuned Amplifiers Second order LCR resonator Second order Active Filters based on Inductor Replacement

Signal Generators Oscillators

October 19, 2007

1

EE 359 Electronic Circuits

HW

Due today 12.7, 12.9,12.28, 12.34 Review October 26 Quiz#2 October 29

October 19, 2007

2

EE 359 Electronic Circuits

Second Order LCR Resonator

• LCR Resonator V0 1 1 = = I Y 1 / sL + sC + 1 / R s/C = 2 s + s (1 / CR ) + 1 / LC

ω 02 = 1 / LC ω 0 / Q = 1 / CR ω 0 = 1 / LC Q = ω 0CR

• Excite parallel LCR resonator – Determine natural modes (I.e. poles of response function)

October 19, 2007

3

EE 359 Electronic Circuits

Transmission Zeros LPF

• Where to inject iput signal Vi ? T ( s) =

V0 ( s ) Z 2 ( s) = Vi ( s) Z1 ( s) + Z 2 ( s )

• Transmission zeros are when Z2(s) are zero (if Z1

October 19, 2007

4

EE 359 Electronic Circuits

Realization of Low Pass Function

• Transmission zeros are when series impedance becomes infinite. 1 sL → ∞ ⇒ s → ∞ ⇒ →0 sC + 1 / R V0 Z2 Y1 1 / sL T ( s) = = = = Vi Z1 + Z 2 Y1 + Y2 1 / sL + sC + 1 / R

October 19, 2007

5

EE 359 Electronic Circuits

High Pass Filter

• Use the series capacitor. Transmission zero at s=0 (dc), shunt inductor is a tranmission zero at s=0. V0 a2 s 2 T ( s) = = 2 Vi s + s( ω 0 / Q ) + ω 02

October 19, 2007

6

EE 359 Electronic Circuits

Bandpass Filter

• Zero at s=0 due to shunt inductor, s=infinity due to shunt capacitor. T ( s) =

V0 s (1 / CR ) = 2 Vi s + s (1 / CR ) + 1 / LC

October 19, 2007

7

EE 359 Electronic Circuits

Inductance Simulation

• Use opamps instead of inductor!

October 19, 2007

8

EE 359 Electronic Circuits

Low Pass Filter

V0 ( s ) Z 2 ( s) T ( s) = = Vi ( s ) Z1 ( s ) + Z 2 ( s )

V0 Z2 Y1 1 / sL T ( s) = = = = Vi Z1 + Z 2 Y1 + Y2 1 / sL + sC + 1 / R October 19, 2007

9

EE 359 Electronic Circuits

High Pass Filter



V0 a2 s 2 T ( s) = = 2 Vi s + s( ω 0 / Q ) + ω 02

October 19, 2007

10

EE 359 Electronic Circuits

Bandpass Filter



T ( s) =

October 19, 2007

V0 s (1 / CR ) = 2 Vi s + s (1 / CR ) + 1 / LC 11

EE 359 Electronic Circuits

Low Pass Notch filter



October 19, 2007

12

EE 359 Electronic Circuits Second-order narrow-band bandpass filter by transforming a Second-order narrow-band first-order low-pass filter bandpass filter by transforming a first-order low-pass filter. (a) Pole of the first-order filter in the s-plane. (b) Applying the transformation s = p + jω0 and adding a complex conjugate pole results in the poles of the secondorder bandpass filter. (c) Magnitude response of the firs-order low-pass filter. (d) Magnitude response of the second-order bandpass filter.

October 19, 2007

13

EE 359 Electronic Circuits Poles and the frequency response of a fourth-order stagger-tuned narrow-band bandpass amplifier by transforming a second-order lowpass .

October 19, 2007

14

EE 359 Electronic Circuits

SIGNAL GENERATORS /OSCILLATORS

A positive-feedback loop is formed by an amplifier and a frequency-selective network In an actual oscillator circuit, no input signal will be present

October 19, 2007

15

EE 359 Electronic Circuits

Oscillator-frequency stability

October 19, 2007

16

EE 359 Electronic Circuits

Limiter Ckt Comparator

October 19, 2007

17

EE 359 Electronic Circuits

Wien-bridge oscillator

without amplitude stabilization .

October 19, 2007

18

EE 359 Electronic Circuits

Wien bridge w/ Amp. Stabil.

limiter used for amplitude control.

October 19, 2007

19

EE 359 Electronic Circuits

Alternate Wien bridge stabil.

October 19, 2007

20

EE 359 Electronic Circuits

Phase Shift Oscillator

October 19, 2007

21

EE 359 Electronic Circuits

Phase Shift. Osc. W/ Stabil.

October 19, 2007

22

EE 359 Electronic Circuits

Quad Osc. Circuit

October 19, 2007

23

EE 359 Electronic Circuits

Active Tuned Osc.

October 19, 2007

24

EE 359 Electronic Circuits

OPAMP based Tuned Amp. Osc.

October 19, 2007

25

EE 359 Electronic Circuits

Colpitts and Hartley Oscillators

October 19, 2007

26

EE 359 Electronic Circuits

Equiv. Ckt

To simplify the analysis, neglect Cm and rp Consider Cp to be part of C2, and include ro in R.

October 19, 2007

27

EE 359 Electronic Circuits

Collpits Oscillator

October 19, 2007

28

EE 359 Electronic Circuits

Piezzoelectric Crystal

October 19, 2007

29

EE 359 Electronic Circuits

Pierce Oscillator

CMOS inverter as an amplifier.

October 19, 2007

30

EE 359 Electronic Circuits

Bistable Operation

October 19, 2007

31

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