UM9552

580 Pleasant St. Watertown, MA 02472 PH: (617) 926-0404 FAX: (617) 924-1235 UM9552 Features Low Frequency Attenuator HF/LF Band Operation Long Lifetime (70 µ s typ.) Very Low Distortion (IP3 @ 455 KHz = < 60 dBm) PIN DIODE ATTENUATOR Description The UM9552 is a very long minority carrier lifetime (70 µ s typical) PIN DIODE that has been developed for low HF or LF Band Attenuator Applications. They have been evaluated for attenuator linearity 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. TYPICAL POWER LEVEL vs FORWARD BIAS CURRENT 40 f1 = F +/- 1 KHz f2 = F +/- 1 KHz 35 65 70 POWER LEVEL/TONE (dBm) 500KHz 250KHz 150KHz 25 55 20 50 TAU = 0.1 ms 15 1 2 3 4 5 6 7 8 10 If NEEDED TO OBTAIN AN IM3 OF - 60 dBc (mA) 45 Electrical Specificat...