A high impedance voltage buffer for wideband measurements

The design of a voltage buffer to interface high impedance source with low impedance load (the measurement instrument) is discussed. The key features are: high input impedance (with low input capacitance), large bandwidth, constant gain and negligible phase delay. The attention is focused on circuit complexity, power consumption and on the possibility of buffer characterization without the need for complex measurements or expensive test equipment. Some versions of the voltage buffer were built and experimentally tested both in time domain and frequency domain.