High-frequency Digital-to-Analog Converters (DACs) require a low-distortion output amplifier to retain the SFDR performance into real-world loads. Figure 8-16 illustrates a single-ended output drive implementation. In this circuit, only one side of the complementary output drive signal is used. The diagram shows the signal output current connected into the virtual ground-summing junction of the OPA4830, which is set up as a transimpedance stage or I-V converter. The unused current output of the DAC is connected to ground. If the DAC requires the outputs to be terminated to a compliance voltage other than ground for operation, then the appropriate voltage level can be applied to the noninverting input of the OPA4830.

Figure 8-16 Wideband, Low-Distortion DAC Transimpedance Amplifier

The dc gain for this circuit is equal to R_F. At high frequencies, the DAC output capacitance (C_D) produces a zero in the noise gain for the OPA4830 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, this pole in the feedback network can be set to:

Equation 8.

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

Equation 9.