The effective amplifier input impedance, Z′a, is connected in series to Z′e, which includes the actual input impedance of the amplifier Za and the shunting paths to ground outside the amplifier (Rs and Cs). Input amplifiers are designed to have a high Za (above 10 MΩ at 1 kHz) to limit the influence of Za on the measured voltage (Robinson, 1968). The shunt resistance (Rs) is usually negligible, but the shunt capacitance (Cs) reduces Z′a, especially at higher frequencies (Robinson, 1968; Nelson et al., 2008). Cs is the combination of all capacitances from connectors and wires from the bath to the amplifier, and the capacitance from metal of the electrode (through the insulation) to the bath (Robinson, 1968). The ratio of Z′e (mostly Ce) and Z′a is of importance, so if the electrode impedance is low enough, the influence of shunt capacitance to the signal is small (Robinson, 1968; Nelson et al., 2008). HDMEAs require small electrodes to achieve a high resolution, and therefore also the Ce is usually small. However, monolithic integration allows keeping Cs small too. For example,
