High Frequency Switch

This is high frequency switch circuit. This circuit uses the 2N4391. When it is off, it will provide a high off-impedance (<0.2pF) and low on-resistance of 30 ohm. Here is the circuit :

This circuit has attenuation > 80dB @ 100 MHz and insertion loss about 6 dB. It can be immediately achieved if we use an “ideal” switch and proper layout. [Source: National Semiconductor Application Note]