AD668

The AD668 is an ultrahigh speed, 12-bit, multiplying digital-to-analog converter, providing outstanding accuracy and speed per-formance in responding to both analog and digital inputs. TheAD668 provides a level of performance and functionality in amonolithic device that exceeds that of many contemporary hy-brid devices. The part is fabricatedusing Analog Devices'Complementary Bipolar (CB) Process, which features verticalNPN and PNP devices on the same chip without the use ofdielectric isolation. The AD668's design capitalizes on this pro-prietary process in combination with standard low impedancecircuit techniques to provide its unique combination of speedand accuracy in a monolithicpart.

The wideband reference input is buffered by a high gain, closedloop reference amplifier. The reference input is essentially a 1 V,high impedance input, but trimmed resistive dividers are pro-vided to readily accommodate 5 V and 1.25 V references. Thereference amplifier features an effective small signal bandwidthof 15 MHz and an effective slew rate of 3% of full scale/ns.

Multiple matched current sources and thin film ladder tech-niques are combined to produce bit weighting. The output rangecan nominally be taken as a 10.24 mA current output or a 1.024 Vvoltage output. Varying the analog input can provide modulationof the DAC full scale from 10% to 120% of its nominal value.Bipolar outputs can be realized through pin-strapping to providetwo-quadrant operation without additional external circuitry.

Laser wafer trimming insures full 12-bit linearity and excellentgain accuracy. All grades of the AD668 are guaranteed mono-tonic over their full operating temperature range. Furthermore,the output resistance of the DAC is trimmed to 100± 1.0%.

The AD668 is available in four performance grades. TheAD668JQ and KQ are specified for operation from 0 to+70, the AD668AQ is specified for operation from 40 to+85, and the AD668SQ specified for operation from 55to +125. All grades are available in a 24-pin cerdip (0.3"package.