Behavior of bulk micromachined silicon flow sensor in the negative differential resistance regime

The performance of a bulk micromachined silicon Row sensor in the negative differential resistance (NDR) regime is investigated for air flow measureme nts. The NDR regime of operation is obtained by boosting the pulse height i n typical pulse mode operation. Our measurements show that operation in the NDR regime results in increased sensitivity compared to operation in the s aturation regime. The increased sensitivity in this regime occurs at relati vely higher temperatures with a possible increase in power consumption. In the pulse mode of operation, with a 3 mA, 100 ms pulse, the unamplified lin ear sensitivity is 40 mVs m(-1) for the how velocities in the range of 5.3- 21.0 m s(-1). In the NDR regime with a 6 mA, 100 ms pulse, the latter is 67 mVs m(-1) for the same flow velocity range. In addition, driving the senso r into the NDR regime results in a response curve (impulse shaped) which sh ows the potential use of different parts of the pulse response to ascertain flow information. Furthermore, for the first time, we report here the puls e type output voltage made possible in the NDR regime for a continuous curr ent input to the sensor.