The IDT F1978 Digital Step Attenuator (DSA) featuring Glitch-Free™ technology improves system reliability and settling time.  It has an attenuation range of 31.5dB with excellent accuracy and very low distortion and insertion loss. The product supports new Direct serial mode programming as well as Conventional serial programming and Parallel programming modes of Direct and Latched.
The F1978 DSA has identical RF performance as the F1975 DSA. The difference between F1978 and F1975 is that F1978 has an additional programming mode called Direct Serial Programming. Consult the "Programming" section of the F1978 datasheet or application note AN-945 “Comparison of F1975 and F1978 Digital Step Attenuator Serial Programming Methods”.


  • 5MHz to 3000MHz frequency range
  • Glitch-Free™ low transient overshoot
  • Low insertion loss 1.2dB at 1GHz
  • Excellent linearity +64dBm IIP3
  • Attenuation step error 0.1dB at 1GHz
  • Serial and parallel interface 31.5dB range
  • Low spurious design
  • 3V / 5V supply, 1.8V / 3.3V control logic
  • Fast settling time
  • Class 2 JEDEC ESD (2kV HBM)
  • 4 x 4 mm 20-TQFN package

Product Options

Part Number Part Status Pkg. Type Lead Count (#) Temp. Grade Pb (Lead) Free Carrier Type Buy Sample
Active VFQFPN 20 K Yes Tray
Active VFQFPN 20 K Yes Reel

Documentation & Downloads

Title language Type Format File Size Date
Datasheets & Errata
F1978 Datasheet Revision O Datasheet PDF 3.77 MB
User Guides & Manuals
RF Product Selection Guide Guide PDF 3.64 MB
Application Notes & White Papers
AN-945 F1975-1978 Serial Programming Methods Application Note PDF 193 KB
AN-896 RF Products EVS Digital Control Software Guide Application Note PDF 3.17 MB
F1978 S-parameters Model - S-Parameter ZIP 869 KB
RF Digital Control Software Installer Software Tool ZIP 169.81 MB
Digital Step Attenuators 日本語, 简体中文 Product Brief PDF 1.07 MB

Boards & Kits

Part Number Title Type Company
F1978EVBI Evaluation Board for F1978, 6-bit, 75 Ohm, Digital Step Attenuator Evaluation Renesas