Hi everyone,
I'm new to this forum and new to audioDIY. Currently, I met a problem of using OPA4132 with PCM1794. I used the typical circuit in the figure, it's from TPA6120 datasheet. I have two questions:
1. What is the function of OPA4132 in this circuit, since TPA6120 has an input impedance of 300k ohm, why we need the OPA4132 as the IV section?
2. What do I expect to observe at -INB and OUTB in the oscilloscope? What I observed is opposite DC voltage but AC signal with the same phase, this seems not right.
Could someone explain the circuit with details, any tips can help?
I'm new to this forum and new to audioDIY. Currently, I met a problem of using OPA4132 with PCM1794. I used the typical circuit in the figure, it's from TPA6120 datasheet. I have two questions:
1. What is the function of OPA4132 in this circuit, since TPA6120 has an input impedance of 300k ohm, why we need the OPA4132 as the IV section?
2. What do I expect to observe at -INB and OUTB in the oscilloscope? What I observed is opposite DC voltage but AC signal with the same phase, this seems not right.
Could someone explain the circuit with details, any tips can help?
Attachments
I am non digital so expect a mistake or three, read at your own risk:
the two output signals IoutL- and IoutL+ are current outputs but with opposite phase.
The first two opamps convert the current output into a voltage output (IV conversion).
These two outputs are still of opposite phase.
The last opamp sums the two out of phase signals into a single ended (unbalanced) voltage output.
Repeat for the right channel.
the two output signals IoutL- and IoutL+ are current outputs but with opposite phase.
The first two opamps convert the current output into a voltage output (IV conversion).
These two outputs are still of opposite phase.
The last opamp sums the two out of phase signals into a single ended (unbalanced) voltage output.
Repeat for the right channel.
the I/V converter circuits' inputs are "virtual ground" - shouldn't see any (<1mV audio) signal there if the circuit is working correctly
quad op amps are not so popular today - many more parts offered in duals, with surface mount the usual challenge is getting all of the passive parts close enough to the chip - dual op amps are a good compromise with singles used when crosstalk in the package is a concern
quad op amps are not so popular today - many more parts offered in duals, with surface mount the usual challenge is getting all of the passive parts close enough to the chip - dual op amps are a good compromise with singles used when crosstalk in the package is a concern
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