1. It is measured by connecting the electrodes to a voltage amplifier . 2. Voltage amplifiers and current amplifiers have different topologies for best noise characteristics.3. Often this circuit is selected when a voltage amplifier is wanted at the output. 4. Voltage amplifier valves not operating at high power are not affected in this way.5. Practically all commercial audio amplifiers are voltage amplifiers . 6. Op-amps are differential voltage amplifiers with very high gain ( sometimes modeled as infinite gain ). 7. A feedback voltage amplifier using an op amp with finite gain but infinite input impedances and zero output impedance. 8. A simple example of the use of feedback is the op-amp voltage amplifier shown in the figure. 9. The common base circuit stops behaving like a voltage amplifier and behaves like a current follower, as discussed next. 10. So, for example, an op amp ( voltage amplifier ) can be arranged to make a current amplifier instead.