Format of Filter Quiz (2013 update)

You will be asked to design a VCVS bandpass or band-reject filter. Your answer will be based on the lecture and online lecture notes on filters, reading the first part of chapter 5 of Horowitz and Hill, and the Matlab function VCVSfilt4.m in a script set up you. For the quiz you should have access to a computer running Matlab; you can also refer to any notes you like.

We will set you up with a Matlab script template in a folder on the Matlab path in a folder like:
\MatlabR12\Work\FiltQuiz.
Your modifications to the script will "self document" your answer.
Your script will call function VCVSfilt4 in the solution to your problem. VCVSfilt4 is a Read Only file that solves for R1=R2, K, and Vout(freq) when you supply it with a frequency range, center frequency, capacitance, filter type and filter name. In Matlab type at the command line >>
help VCVSfilt4
to
read the documentation about the function.

The specifications in your call to design will
* tell you whether it's bandpass or band-reject filter
* imply that Bessel, Chebyshev or Butterworth would be the "type" of filter
* set limits on gain for the edges of the pass or reject region
* set a limit on gain for the middle of the freuency pass region
* tell you the size of all the capacitors you can use in the design
* tell you that the gain-setting "K" resistors R are 10K ohms
* ask you to show the spectrum (plotted in VCVSfilt4) of the gain with log freq vs linear gain
* ask you to draw out the circuit, using no more than a certain number of op amps, and showing all resistance value and
showing what sub-circuit joins the LP and HP parts of the filter.

If you can't meet the specs with 1 LP and 1 HP filter consider putting 2 filters in series to increase the sharpness of a cutoff.

Your answer--script, spectrum and circuit diagram--must be presented in person to JDD or a TA for inspection and approval.

Examples of filter quizzes:

% design a maximally sharp bandreject filter such that
% at 36Khz the gain is greater than 1.25 and
% at 200KHzKHz the gain is less than 0.3
% and at 650KHz the gain is greater than 1.1
% no gain in spectrum greater than 2.5
% use only 0.003 muF capacitors
% gain setting resistor is R = 10K for VCVS template on p. 274 of H&H
% show spectrum meeting specs in form of semilogx plot with linear gain on y axis
% draw a circuit diagram of LP and HP components and
% show how the LP and HP are combined or connected together for a
% final Vout whose gain w.r.t. Vin is spec'd above
% include ALL resistance values in ohms. no more than 14 op amps allowed.
% if spectrum is valid for 3 consecutive tries of res_flg == 1, then +2 point bonus.

% design a maximally sharp gain curve bandpass filter such that
% at 24Khz the gain is less than 0.2 and
% at 95KHz the gain is less than 1.2
% and at 580KHz the gain is less than 0.22
% no gain in the pass band greater that 2.7

% use only 0.05 muF capacitors
% gain setting resistor is R = 10K for VCVS template of p. 274 H&H
% show spectrum meeting specs in form of log freq vs gain plot
% draw a circuit diagram of LP and HP components
% show how the LP and HP are combined or connected together for a
% final Vout whose gain w.r.t. frequency is spec'd above
% include ALL resistance values in Ohms. no more than 10 op amps allowed.
% if res_flg == 1 and the spectrum is valid for 3 consecutive tries, then 2 point bonus

Real Resistor bonus. If you set the last argin of VCVSfilt4--res_flg--to 1 the program will call function Nearest_Rstd which will find the nearest resistor in a bin of 13 resistors per decade; it will then randomly alter that resistance RR by +/- 5%; it will also alter the given capacitance CC by +/- 20%; if your spectrum still meets the specs after running res_flg == 1 3 times in a row, you will receive a 2 point bonus (on the A-path).

Filter Quiz answers given after Thanksgiving will receive half credit on the A-path.