Variable Attenuator

This is a variable attenuator circuit. This circuit can be used to reduce the power or amplitude of a signal without appreciably distorting its waveform. Here is the circuit :

This circuit uses 2N3685 as a voltage variable resistor with an RDS(on) of 800 Ohm. Using 2N3685 JFET, this circuit will provide excellent electronic gain control because 2N3685 has linear resistance over several decades of resistance. [Source: National Semiconductor Application Note]