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Please see/find my enclosed file for the schematic.I want to build my own analog stage for my minidisc player (which I use as a DAC.)
The DAC has 2 output's per channel, therefore I want to have a differential buffer and then a gain stage.I am no EE and barely know how these opamps work so I copy designs and put them together
Will my design work? Any thought's on the design are appreciated (Except op-amp fetishes) It uses the TLE2027AI opamp. The only thing I don't want to change with this design
is the opamp. Cause I have a couple of them lying aroundRegards,
Bas Horneman.
Follow Ups:
Hi,Sorry, your design will not work - at least not as intended.
1) Your differential stage needs two additional resistors, one in each input branch. If you don't want any gain in the differential stage, all four resistors should have the same value (in your case 10k).
2) The gain stage also need an additional resistor (connected between the output of the diff stage and the - input of the gain stage). (I am calling this resistor R4 for later reference). The value of this will define the gain. Choosing - for example - 5k for R4 will give you a gain of 2 (actually Gain = - R3 / R4; the minus sign means that the output is inverted compared to the input).
There is several additional points to make:
I assume that your DAC is a voltage (not current) output device. If that is not the case the differential stage need to look a little bit different. (Current output DAC's are mainly a thing of the past, but they still exist).
The output of the first amp need to drive current both through the feedback resistor R1 and R4. Both these resistors will behave as connected to ground, so you have to pay attention to the output current of first amp, especially if you need a high gain. You should avoid getting R1 // R4 lower than 2k.
Normally, a non-inverting gain stage will give slightly better performance than the inverting you are using.
I suggest you look at Texas Instrument homepage. They do have a lot of application notes - some of it god but basic stuff about using opamps. You may start looking for an application note sboa-92a.pdf.
Regards,
Torbjorn Eriksson
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