EE 435 Lect 44 Spring 2010

EE 435 Lect 44 Spring 2010 - EE 435 Lecture 44 Integrated...

Info iconThis preview shows pages 1–13. Sign up to view the full content.

View Full Document Right Arrow Icon
EE 435 Lecture 44 Integrators OTA-C Filters Switched-Capacitor Filters Voltage Amplifiers Integrated Filters and Amplifiers
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Typical Filter Implementation T 1 (s) Biquad T 2 (s) Biquad T k (s) Biquad V OUT V IN T m (s) Biquad T 0 (s) First- Order I 1 (s) Integrator I 2 (s) Integrator I 3 (s) Integrator I 4 (s) Integrator I k (s) Integrator V IN V OUT I k-1 (s) Integrator a 2 a 1 Biquads often LP or BP .• •• Review from last lecture .•
Background image of page 2
Typical Biquad Implementation (Two-Integrator Loop) ( ) 2 0 22 0 0 I Ts s + I s+I α = 0 I s 0 I s + X IN X OUT α Accurate control of I 0 and α is essential for building most filters ! .• •• Review from last lecture .•
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Observation: • The integrator is the key building block in most filters • Accuracy of I 0 and α is important ! .• •• Review from last lecture .•
Background image of page 4
RC Biquadratic Filter R A R A R R R Q C R 1 C V IN V OUT 0 0 I s+ αI 0 I s + X IN X OUT 1 .• •• Review from last lecture .•
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
What happens if accuracy is not attained? Unacceptable performance (variability in I 0 orders of magnitude too large!) No market opportunity ! ω Desired Response Actual Response With process variations of +/- 20% in sheet resistance and another +/-15% variation in resistance with temperature, variability of R is several orders of magnitude too large 0 1 I= RC Process variations in C are in the +/- 20% range as well
Background image of page 6
Economic Implications V IN V OUT R C 0 1 I= RC If I 0 =1KRad/Sec and C=1pF, how large must R be? 9 10 0 1 R= IC = If sheet resistance is 30 ohms/square, one resistor requires 33 million squares ! .• •• Review from last lecture .•
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Challenges in Integrated Filter Design • Accuracy of components is not good enough (orders of magnitude) • Area too large for audio frequencies (orders of magnitude) .• •• Review from last lecture .•
Background image of page 8
Challenges in Integrated Filter / Integrated Integrator Design C R V IN V OUT ( ) 1 Ts - RCs = 0 1 RC I = •Accuracy of R and C difficult to accurately control – particularly in integrated applications •Size of R and C unacceptably large if I 0 is in audio frequency range •Amplifier GB limits performance .• •• Review from last lecture .•
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Consider the following two circuits ( ) SC 1 IN 1 Q = C t −• V V OUT V IN C 1 C φ 1 φ 2 T t 1 t 1 +T φ 1 φ 2 V IN V OUT R C ( ) IN 1 RC t QT R V RC SC QQ EQ 1 T R C Thus equating charges Obtain the equivalent resistance of the switched-capacitor circuit .• •• Review from last lecture .•
Background image of page 10
Thus, if clocked with a clock period of T, for T<<T SIG , we have to following equivalence T t 1 t 1 +T φ 1 φ 2 EQ 1 T R C C 1 φ 1 φ 2 R EQ Equivalence of a switched capacitor and a resistor has been known for over 100 years Up until 1977, this knowledge of little practical significance .• •• Review from last lecture .•
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The switched-capacitor integrator V OUT V IN C 1 C φ 1 φ 2 T t 1 t 1 +T φ 1 φ 2 V IN V OUT R C EQ 1 T R C Accuracy of R and C difficult to accurately control – particularly in integrated applications
Background image of page 12
Image of page 13
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/31/2012 for the course EE 345 taught by Professor Geiger during the Fall '11 term at Iowa State.

Page1 / 71

EE 435 Lect 44 Spring 2010 - EE 435 Lecture 44 Integrated...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online