Non-linear circuits and sensors

Size: px

Start display at page:

Download "Non-linear circuits and sensors"

Conrad Fowler
5 years ago
Views:

1 ELEC3106, Electronics Non-linear circuits and sensors 1 ELEC3106 Electronics: lecture 10 summary Non-linear circuits and sensors Torsten Lehmann School of Electrical Engineering and Telecommunication The University of New South Wales UNSW Sydney 2052, Australia

2 ELEC3106, Electronics Non-linear circuits and sensors 2 Oscillators Soft amplitude limiting amplifier A = 1 = 1 + R 2 V P R1 R 2 = R 2A for small R 2 = R 2A R 2X for large Wien-bridge oscillator (incremental) V s2 + 3 O1 RC s + 1 (RC) = (A 1)R 2 i 1 n s A RC s + 1 (RC) 2 ω 0 = 1 RC Q = 1 3 A oscillates for A > 3 R R 1 Limiting amplifier V P i n C V I 1 Positive feedback R R 2A C Frequency selection f V CC R 2T V EE 2 R 2X 1 R 2X R 2T = V CC

3 ELEC3106, Electronics Non-linear circuits and sensors 3 Pierce oscillator X-tals (piezoelectric crystals) equivalent L large may be > 100H equivalent C S small may be < 1fF series resonance ω 0 = 1/ LC S Q very large ω 0 very stable and well defined V B C P L X r C S ω Pierce oscillator inverter biased as amplifier C 1 -X 1 -C 2 pi-filter resonance ω 0 = 1/ L(C S C 2 ) 1/ LC S Loop gain L AA (ω 0 ) g m R O C S /C 2 g m V A V A R O R f V B R1 V B ω 0 t C 2 X 1 C 1 V A t

4 ELEC3106, Electronics Non-linear circuits and sensors 4 Hysteretic oscillator Schmitt trigger = H,L V TH = R 1 R 1 + R 2 H V TL = R 1 R 1 + R 2 L Hysteretic oscillator for H = V ( OL ) 2R1 + R T = 2RC ln 2 R 2 R 1 V X R 2 C R H V TL V X L V TH Voltage controlled oscillator (VCO) e.g. replace R with FET V X V TH t V TL T

5 ELEC3106, Electronics Non-linear circuits and sensors 5 Multiplier Gilbert multiplier I O1 I O2 = ( ) ( ) VA1 V I B tanh A2 VB1 V tanh B2 2V T 2V T I O1 I O2 ( )( ) VA1 V I A2 VB1 V B2 B 2V T 2V T V B1 V A1 I O1 V B2 I B I O2 V B1 V A2 Mixers Phase detectors V Sig f V RF f Gain control 4kHz 2.4GHz Signal conditioning V Sig V RF V 1 sin(ω t) power amp

6 ELEC3106, Electronics Non-linear circuits and sensors 6 Phased-locked loop Phase detector V 1 = V 1A sin(ω 1 t), V 2 = V 2A cos(ω 2 t) φ 1 = ω 1 t, φ 2 = ω 2 t V 1 φ 1 V X φ 1 φ 2 V X = KV 1 V 2 = 1 2 KV 1AV 2A (sin(ω 1 t ω 2 t) + sin(ω 1 t + ω 2 t)) V 2 φ KV 1AV 2A sin(ω 1 t ω 2 t) (low-pass filter) 1 2 KV 1AV 2A (ω 1 t ω 2 t) Phased-lock loop locks in at zero frequency error clock multiplication demodulation clock extraction clock synchronisation f In Filter A Counter VCO f Out

7 ELEC3106, Electronics Non-linear circuits and sensors 7 Automatic gain control Ideal signal rectification V I V R V R Peak detector Automatic gain control (AGC) increase gain gradually decrease gain fast reduces dynamic range V I V I V R t V In ut Gain control increase decrease V Low V High Peak detect

8 ELEC3106, Electronics Non-linear circuits and sensors 8 High input impedance Instrumentation amplifier High differential gain = ( 1 + R ) 4 R2 (V R 3 R 2 V 1 ) 1 Good common-mode rejection V 1 R 4 V 1A R 1 R 2 Good noise performance 2 R 3 R 4 V 2A R 1 R 2 V 2

9 ELEC3106, Electronics Non-linear circuits and sensors 9 Apply suitable bias conditions Detect sensor signals Sensor interfaces Filter and amplify signals for further processing V B Potentiostat integrator applies bias voltage measures minuscule electrode current I E integrates current (reduces noise and amplifies signal) CE WE V E H + I E

10 ELEC3106, Electronics Non-linear circuits and sensors 10 Datasheets 74LVC1GX04 X-tal driver LM555 Timer IC NB3N502 PLL clock multiplier INA826 Instrumentation amplifier ADA4051 Chopper stabilised op-amp

Hours / 100 Marks Seat No.

Hours / 100 Marks Seat No. 17445 21415 3 Hours / 100 Seat No. Instructions (1) All Questions are Compulsory. (2) Illustrate your answers with neat sketches wherever necessary. (3) Figures to the right indicate full marks. (4) Assume