R-RC circuit

Figure 4 (a) R-RC equivalent analog circuit diagram, showing conduction paths 1 and 2. (b) Impedance response of R-RC circuit on the complex plane. The arrow indicates the direction of increasing frequency. The frequency at the apex of the arc (CO ) is related to the time constant (/ ) of the circuit. 

The impedance response of the R-RC circuit in Figure 4a is illustrated on a complex plane plot in Figure 4b. At low frequencies, the data approach the real axis at R + Rp (pathway 2), and the capacitive response is illustrated by the arc in the data. The frequency at the apex of the arc (to ) corresponds to the characteristic relaxation time (f ) of the circuit ... 

Fig. 3.16 Simulated impedance spectra (Bode plots) for the R(RC) circuit from Fig. 3.12c. The simulation includes a simple model that describes the bandwidth limitation of a (hypothetical) potentiostat. Several parameters are varied (a) the range resistor, Ri, (b) the depletion layer thickness W (c) the sample diameter ) (d) the resistance parallel to the space charge capacitance, Rsc- The series resistance Rs is fixed at 140 Q and Csc is calculated using Csc = (so Af h where Sr is the dielectric constant (25) and the surface area A is given by ll4nD. Note that the simulation in (a) does not show the increase in noise that one expects at less sensitive current ranges...

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