High-frequency video digital-to-analog converters (DACs) sometimes benefit from a low distortion output amplifier to retain the SFDR performance into real-world loads. Figure 8-14 shows a differential output drive implementation. The diagram shows one or more of the signal output currents connected into one or more of the virtual ground summing junctions of the OPA2830, which is set up as a transimpedance stage or I-V converter. If the DAC outputs require to terminate to a compliance voltage other than ground for operation, the appropriate voltage level can be applied to the noninverting input of the OPA2830. The dc gain for this circuit is equal to R_F. At high frequencies, the DAC output capacitance (C_D in Figure 8-14) produces a zero in the noise gain for the OPA2830 that can cause peaking in the closed-loop frequency response. C_F is added across R_F to compensate for this noise gain peaking. To achieve a flat transimpedance frequency response, the pole in each feedback network can be set to:

Equation 4.

which gives a cutoff frequency f_–3dB of approximately:

Equation 5.

Figure 8-14 High-Speed DAC—Differential Transimpedance Amplifier