1. The problem statement, all variables and given/known data We have a filtered amplifier (diagram is attached). We do not know Cf or Rf. We know that: 1 volt input at 5 Hz = 9.25 volt output 1 volt input at 200 Hz = 6.77 volt output 1 volt input at 500 Hz = 3.66 volt output 2. Relevant equations The transfer function for the first amplifier is H(w) = -Zf/Zi = -10000/2000=-5 The transfer function for the second amplifier is H(w) = -Zf/Zi, where Zi = 5000 and Zf = Rf/(Rf j w Cf + 1). 3. The attempt at a solution If we multiply the two transfer functions above, we obtain H(w) = V0/Vi = Rf/(1000(Rf j w Cf + 1)) I multiplied the frequencies by 2*pi and made appropriate substitutions in the above equation to get the following three expressions: 9.25 = Rf/(1000(31.4159 Rf j Cf + 1)) 6.77 = Rf/(1000(1256.64 Rf j Cf + 1)) 3.66 = Rf/(1000(3141.59 Rf j Cf + 1)) Three equations for only two unknowns? I get that Cf = -5.3E-8 i and Rf = 9395. What am I doing wrong?