IH401A

• rDS(ON) (Typ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35W
• ID(OFF) (Typ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10pA
• Switching Times (R_L = 1kW)
- tON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25ns
- tOFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75ns
• Built-In Overvoltage Protection . . . . . . . . . . . . . . ±25V
• Charge Injection Error (Typ) into 0.01mF Capacitor . . 3mV
• CISS (Typ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <1pF
• Can Be Used for Hybrid Construction

The IH401A is made up of 4 monolithically constructed combinations of varacitor type diode and a N-Channel JFET. The JFET itself is very similar to the popular 2N4391, and the driver diode is specially designed, such that its capacitance is a strong function of the voltage across IH401A. The driver diode IH401A is electrically in series with the gate of the N-Channel FET and simulates a back-to-back diode structure. This structure is needed to prevent forward biasing the source-to-gate or drain-to-gate junctions of the JFET when used in switching applications.

Previous applications of JFETs required the addition of diodes, in series with the gate, and then perhaps a gate-tosource referral resistor or a capacitor of IH401A in parallel with the diode; therefore, at least 3 components were required to perform the switch function. The IH401A does this same job in one component (with a great deal better performance characteristics).

Like a standard JFET, the practically perform a solid state switch function translator IH401A should be added to drive the diode. This translator takes the TTL levels and converts IH401A to voltages required to drive the diode/FET system (typically a 0V to -15V translation and a 3V to +15V shift). With ±15V power supplies, the IH401A will typically switch 22VP-P at any frequency from DC to 20MHz, with less than 50W rDS(ON).