K =  1.3806503e-23
Q = 1.60217646e-19 

class Interpolate
  def initialize
    @values = []
  end
  def [](x0)
    j, k = -1, -1
    @values.each_with_index do |(x, y), i|
      j = i if x0 >= x
      k = i if x0 < x and k == -1
    end
    raise "can't interpolate :-( (lower bound?)" if j == -1
    raise "can't interpolate :-( (upper bound?)" if k == -1
    x1, y1 = @values[j]
    x2, y2 = @values[k]
    return (x0 - x1) * (y2 - y1)/(x2 - x1) + y1
  end
  def []=(x, y)
    @values += [[x.to_f, y.to_f]]
    @values = @values.sort
  end
end

class Resistor
  attr_accessor :ohms, :kelvins
  def vn_root_hz
    Math::sqrt(4 * K * @kelvins * @ohms)
  end
  def to_f
    r.to_f
  end
end

class FirstOrderLPF
  def initialize
    @wc = 1.0
  end
  def wc=(wc)
    @wc = wc.to_f
  end
  def fc=(fc)
    @wc = 2.0 * Math::PI * fc.to_f
  end
  def fc
    @wc / (2.0 * Math::PI)
  end
  def [](f)
    1.0 / Math::sqrt((f / fc) ** 2 + 1.0)
  end
end

class Range
  def logmap(points)
    (1..points).map { |x| first * (last/first) ** ((x-1)/(points.to_f-1)) }
  end
end

opamp_vn = Interpolate.new
opamp_in = Interpolate.new

[
  [10, 20e-9],
  [100, 12e-9],
  [1e3, 11e-9],
  [10e3, 9e-9],
  [101e3, 9e-9],
].each do |(f, a)|
  opamp_vn[f] = a
end

opamp_in[0] = 0.6e-15
opamp_in[101e3] = 0.6e-15

lpf = FirstOrderLPF.new
rf = Resistor.new
rf.ohms = 10e3
rf.kelvins = 295.0
cf = 800e-12
lpf.wc = 1/(rf.ohms * cf)

(10..100e3).logmap(10).each do |f|
  k = lpf[f]
  puts [
          f,
          opamp_vn[f],
          opamp_in[f]*rf.ohms,
          rf.vn_root_hz,
          lpf[f],
      ].map { |x| "%e" % [x] }.join(' ')
end