Figure 4
Measured frequency response of the nanoelectromechanical resonant amplifier. (a) Measurement setup, showing the connection between the network analyzer and the device. (b) amplitude and (c) phase response of a nanoelectromechanical resonant amplifier, operating at 4.2 MHz measured by a network analyzer for a matched load of RL=RA. By increasing the DC bias current, the device makes the transition from attenuation to amplification and finally to oscillation at the resonance frequency, as predicted in Figure 2. At low bias currents, where the device is passive, the phase is zero with an absolute voltage gain of less than one. At the transition from the passive region to the active region, where the device resistance RD is infinite, it is shown that the gain has the strongest downward peak, indicating that little of the input signal passes through the device to the load. In the active region, the peak begins to grow towards amplification with a phase of 180°. On the verge of oscillation, the phase becomes zero again, and the system becomes unstable. (d) Measured frequency response of a 30-MHz electromechanical amplifier, which shows a similar trend.
