I'm using a Maxim DAC (the MAX541) with a TI microcontroller. I output a digital audio signal from the microcontroller to the DAC. I have the DAC's output hooked up to a typical 3.5mm audio jack. When I plug the 3.5mm jack into typical computer speakers the volume is quite low. I have to crank up the speakers to hear the audio.
Hooking up the 3.5mm audio jack to my oscilloscope I see the max peak-to-peak voltage output is only about 0.12 volts:
When I play the same digital audio using my phone at a reasonably loud level and analyze it with my oscilloscope I see the peak-to-peak max voltage is around 1 volt:
When purchasing the MAX541 DAC I suspected it would need some amplification so I also purchased a MAX492 op amp. I have the analog output of the DAC going to the input exactly as shown in the MAX492 datasheet's "typical operating circuit" example:
Here's a link to the MAX492 datasheet.
However, this is only amplifying the signal to a peak-to-peak max of about 0.23 volts. I of course need the MAX492 to amplify the signal to around 1 volt (like my phone's output level), however, I've read through the datasheet and it's not clear to me how to do this or if it's even possible.
Any help would be most appreciated. Thank you.
Best Answer
You have the voltage gain of the opamp at \$Gain = 1 + \frac{10k}{10k} = 2\$ times. If you want the voltage gain to be 8.3 times then use 75k for the negative feedback resistor (R1 in the image below).