嵌入式系统导论-实验课-ex5_review.pdfVIP

Exercise 5: Second-order Low-pass Active Filter Active Filter ? An active filter is a type of analog electronic filter that uses active components such as an amplifier. ? Passive filters: Only R, L, C. Operational Amplifier (OP-AMP) ? Properties of ideal OP-AMP : – Infinite input impedance – Zero output impedance – Infinite open-loop gain – Infinite Common-mode rejection ratio (CMRR) ? Golden rules: – The output attempts to do whatever is necessary to make the voltage difference between the inputs zero. – The inputs draw no current. Open Loop Closed Loop Passive filters Angular frequency not equal to coner frequecny. Active Filter ( Frist Order ) Angular frequency not equal to coner frequecny. The Angular frequecy Active Filter ( Second Order ) Va VpR1 R2 C2 C1 Active Filter ( Second Order ) N(s) is a polynomial which’s order less than or equal to two. Standard form of transfer function for second order system: Denominator can be expressed as: W0 : The cut-off Angular frequency Q : The quality factor Active Filter ( Second Order ) High-Pass: Band-Pass: Low-Pass: T Q