A primer on using PIN diodes in VCAs - Part 2 of this tutorial discusses the pi-configured PIN-diode approach to implement a voltage-controlled attenuator for microwave applications.
01 February 2001
There are many ways to implement a voltage-controlled attenuator (VCA), but it typically involves the use of some variable-impedance device. This variable impedance device can be a metal-semiconductor field-effect transistor (MESFET) operating as a voltage-variable resistance in its linear region, or it can be a PIN diode operating as a current-controlled resistance. PIN diodes offer the advantages of high power-handling capability, more design freedom, low distortion, and low cost. Last month, Part 1 of this tutorial presented two classic microwave design; approaches using one or more PIN diodes-the resistive-line approach and the constant-impedance approach. This month, Part 2 presents the pi -configured, PIN-diode approach, and discusses the advantages and disadvantages of all three designs.