1.3 Constant Resistance Analog Switch

Applications that require a constant ON-resistance over a wide range of analog signals will benefit considerably from the HT0440. Any MOSFET used in conjunction with a HT0440 will exhibit a fixed “ON” state resistance due to the constant value of voltage across the gate and source of the MOSFET switch (see Figure 1-4). This gate-source voltage differential will remain independent of the voltage level and polarity of the analog signal through the switch. Some examples of applications that benefit from this technique are high-end audio, sample and hold, and data conversion circuits.

Figure 1-3 shows a commonly used scheme for most Analog Switch ICs that utilizes an N- and P-channel MOSFET. A major disadvantage of this configuration is that the ON-resistance of the analog switch changes with variations in the amplitude of the signal voltage.