The Krohn-Hite Model 3945 programmable filter provides one Butterworth channel of low-pass, tunable over the range from 170Hz to 25.6MHz; and two independent Butterworth or Bessel channels of low-pass, high-pass or bypass, one channel of band-pass or band-reject, tunable over the range from 3Hz to 2MHz.
The 3945 has been specifically designed for applications requiring high frequency band-pass filtering. The high cutoff may be set to any frequency between 170Hz and 10MHz, and the lower cutoff to any frequency between 3Hz and 2MHz.
One channel of the 3945 can operate as a low-noise amplifier, bypassing the filter, delivering a bandwidth of 50MHz and gains up to 46dB. This is useful to users wanting to increase the gain of the signal and improve signal-to-noise ratio before filtering. The other two channels of the 3945 furnish Bessel or Butterworth transfer functions and can be programmed to operate as two low-pass, high-pass, one band-pass or band-reject filter with gains to 40dB per channel.
The 3945 offers 99 groups of non-volatile memory for storage of front panel set-ups, which are stored in battery-backed CMOS. Set-ups can be recalled with a simple command. Self-test diagnostics occur upon power-up insuring that all internal memory is operating properly. If a failure occurs, the display will indicate which ROM or RAM has failed.