CA3256

The CA3256 BiMOS analog video switch has five channels of CMOS multiplex switching for general-purpose videosignal control. One of four CMOS channels may be selected in parallel with channel 5. The CMOS switches are inputs to the video amplifier but may be used in bilateral switching between channels 1 to 4 and channel 5. The analog switches of channels 1 to 4 are digitally controlled with logiclevel conversion and binary decoding to select 1 of 4 channels. The enable function controls channels 1 to 4 but does not affect channel 5. LED output drivers are selected with the channel 1-to-4 switch selection to indicate the ONchannel. Channel 5 may be used as a monitor output for data or signal information on channels 1 to 4. The transmission gate switches shown in the block diagram of the CA3256 are configured in a "T" design to minimize feedthrough. When the switch is off, the shunt or center of the "T" is grounded.

CA3256 amplifier has high input impedance to minimize the RON transmission gate insertion loss. The amplifier output impedance is typically 5W in a complementary symmetry output. The amplifier can directly drive a nominal 75W coaxial cable to provide line-to-line video switching. The gain of the amplifier is programmable by different feedback resistor values between pins 8 and 9. Compensation may also be used between these pins for an optimally flat frequency response. CA3256 internal regulated 5V bias reference with temperature compensation permits stable direct-coupled output drive and minimizes DC offset during signal switching.