The JFE2140 can be configured as a cascoded JFET front end. Cascode refers to using a second transistor in-series with the input transistor; see Figure 9-2 for an example.

Figure 9-2 JFE2140 connected in Cascode Configuration

Using a cascode configuration, as shown in Figure 9-2, increases the output impedance of the stage, resulting in higher gain, as well as buffers the input node from gate current that flows when the V_DS voltages are higher. The V_BIAS node must be forced to a voltage greater than what is required to allow both JFETs to remain in the saturated region. A JFET is not required to be used as the cascode device; the benefits of cascoding can be realized with other transistor types, while still maintaining the low-noise, high-impedance benefits of the JFE2140.