Many high-performance audio digital-to-analog converters (DACs) feature a current output that must be converted into a voltage output for use with audio amplifiers. In premium automotive audio applications, for example, it is critical that the DAC signal-to-noise ratio (SNR) and total harmonic distortion plus noise (THD+N) performance is not compromised by the current-to-voltage (I-V) output stage. The first stage of the circuit converts the current output to a voltage output by providing a virtual ground potential to the OUTP and OUTN nodes of the DAC. The current flowing from the DAC then creates a voltage across the resistor, R4, R18, in the feedback loop. Note that current-output audio DACs have a common mode current that creates an offset to confirm that the DAC is always sourcing current. This common-mode current also results in the output of the first stage always being a negative value. The supplies of the amplifiers of the circuit are not required to be symmetrical. The second stage of the circuit is a differential amplifier that converts the differential voltage of the first stage into a single-ended output voltage. In the third-order, low-pass filter (LPF) circuit, the output level of 2.1 V RMS and 123-dB signal-to noise ratio is achieved. A NE5534 operational amplifier is used for the I/V circuit to obtain the specified performance. Dynamic performance such as the gain bandwidth, settling time, and slew rate of the operational amplifier affects the audio dynamic performance of the I/V section. The current of the PCM1795 device on each of the output pins (IOUTL+, IOUTL–, IOUTR+, IOUTR–) is 4 mA-PP at 0 dB (full-scale).
Many high-performance audio digital-to-analog converters (DACs) feature a current output that must be converted into a voltage output for use with audio amplifiers. In premium automotive audio applications, for example, it is critical that the DAC signal-to-noise ratio (SNR) and total harmonic distortion plus noise (THD+N) performance is not compromised by the current-to-voltage (I-V) output stage. The first stage of the circuit converts the current output to a voltage output by providing a virtual ground potential to the OUTP and OUTN nodes of the DAC. The current flowing from the DAC then creates a voltage across the resistor, R4, R18, in the feedback loop. Note that current-output audio DACs have a common mode current that creates an offset to confirm that the DAC is always sourcing current. This common-mode current also results in the output of the first stage always being a negative value. The supplies of the amplifiers of the circuit are not required to be symmetrical. The second stage of the circuit is a differential amplifier that converts the differential voltage of the first stage into a single-ended output voltage. In the third-order, low-pass filter (LPF) circuit, the output level of 2.1 V RMS and 123-dB signal-to noise ratio is achieved. A NE5534 operational amplifier is used for the I/V circuit to obtain the specified performance. Dynamic performance such as the gain bandwidth, settling time, and slew rate of the operational amplifier affects the audio dynamic performance of the I/V section. The current of the PCM1795 device on each of the output pins (IOUTL+, IOUTL–, IOUTR+, IOUTR–) is 4 mA-PP at 0 dB (full-scale).
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