UM9552

The UM9552 is a very long minority carrier lifetime (70 ms typical) PIN DIODE that has been developed for low HF or LF Band Attenuator Applications. They have been evaluated for attenuatorinearity and distortion characteristics in a Bridge Tee Attenuator Circuit at 455 KHz (the common intermediate frequency for AM transmitters and receivers). When the UM9552's are used as the two variable resistors in the Bridged Tee Circuit, the Third Order Intermodulation Products are below -60 dBc with 0 dBm input power over an attenuation range of 4 dB to 30 dB.

These thicker, longer lifetime PIN diodes exhibit a more linear forward biased resistance (RS) vs forward bias current (If) relationship, which greatly simplifies the design of the driver circuits that supply the bias currents over the specified attenuation range. This task is simplified if the low attenuation range is truncated and the few dB are compensated by commercially available, inexpensive 4 to 6 dB gain blocks.